Chapter 2 Forces and Motion

Chapter 2 Force And MotionChapter 2 Force And Motion

ITeach – Physics Form 4

2.1 Analysing Linear Motion


Analysing Linear MotionChapter 2 Force And Motion

Linear Motion

Linear motion is the motion of an object whose path is a straight line

Running a 100 m race

An apple falling from tree

A moving bullet

ITeach – Fizik Tingkatan 4

Menganalisis Gerakan LinearBab 2 Daya dan Gerakan

Gerakan Linear

Gerakan linear ialah gerakan ssesuatu objek dalam lintasan lurus atau dalam garis lurus.

Berlari sejauh 100 m

Epal jatuh daripada pokok

Peluru yang sedang bergerak

An athlete ran a 400 m race in a time of 80.0 seconds.



Speed Velocity

A scalar quantity A vector quantity

Speed And

Velocity

Example

Distance ran = 400 m Displacement = zero (0) m Speed = distance / time Velocity = displacement / time

= 400 / 80.0 = 0 / 80.0= 5 m s-1 = 0 m s-1

Rate of change of distance Rate of change of displacement

Speed = distance travelled / time Velocity = displacement / time

Seorang atlet berlari dalam lumba lari 400 m dalam masa 80.0 saat.

ITeach – Fizizk Tingkatan 4


Laju Halaju

Suatu kuantiti skalar Suatu kuantiti vektor

Laju dan

Halaju

Contoh

Jarak berlari = 400 m Sesaran = Sifar (0) m Laju = jarak / masa Halaju = sesaran / masa

= 400 / 80.0 = 0 / 80.0= 5 m s-1 = 0 m s-1

Kadar perubahan jarak Kadar perubahan sesaran

Laju = jarak dilalui / masa Halaju = sesaran / masa



Acceleration And Deceleration

A vector quantity When an object accelerates, its velocity changes.

For an object in linear motionObject accelerating, velocityObject decelerating, velocity

Acceleration, a =

final velocity, v – initial velocity, u

time, t

u is the velocity of an object at the start of its motion

v is the velocity of an object at the end of its motion

a is the rate of change of velocity



Pecutan dan Nyahpecutan

Suatu kuantiti vektor Apabila suatu objek memecut, halajunya berubah.

Objek bergerak dalam garisan linearObjek memecut , halajuObjek nyahpecut, halaju

Pecutan , a =

Halaju akhir, v – Halaju awal, u

Masa, t

u Halaju objek ketika ia mula bergerak

v Halaju objek di akhir gerakan

a Kadar perubahan halaju



Numerical Example Acceleration And Deceleration

A car starts form rest and accelerates uniformly achieving a velocity of 50 m s-1 in a time of 10 seconds.

Initial velocity u = 0 m s-1 (car at rest / stationary) Final velocity v = 50 m s-1

Time t = 10 s

Acceleration, a = v – u t

a = 50 – 0 10

a = 5 m s-2



Contoh BerangkaPecutan dan Nyahpecutan

Sebuah kereta bergerak daripada keadaan rehat dengan pecutan seragam sehingga ia mencapai halaju 50 m s-1 dalam masa 10 saat.

Halaju awal u = 0 m s-1 (kereta dalam keadaan rehat / pegun) Halaju akhir v = 50 m s-1

Masa t = 10 s

Pecutan , a = v – u t

a = 50 – 0 10

a = 5 m s-2



Ticker Timer

Used together with a trolley to study linear motion in the laboratory.

Powered by a 12 V AC power supply of frequency 50 Hertz.

The metal strip (vibrator) vibrates 50 times in 1 second when connected to power.

The vibrating metal strip punches dots on the carbonized ticker tape.

trolleyrunwaytimer

coil

magnet

ticker tape

AC power

vibrating bar

carbon paper disc



Jangka Masa Detik

Digunakan bersama troli untuk mengkaji gerakan linear di dalam makmal.

Satu bekalan kuasa 12 V AC digunakan dengan frekuensi 50 Hertz.

Jalur bergetar bergetar 50 kali setiap 1 saat apabila ia bersambung dengan bekalan kuasa.

Jalur bergetar menebuk titik pada pita detik berkarbon.

trolilandasanJangka

masa

gelung

magnet

Pita jangka masa detik

Kuasa AC

Jalur bergetar

Pita detik berkarbon



The Ticker Tape

• Shows a comprehensive record of the motion of the trolley that pulls the ticker tape through the ticker timer.

• The vibration metal strip makes 51 dots on the ticker tape per second.

• The time interval between two successive dots is called a tick.

dots

1 tick

• 50 ticks are made on the ticker tape in 1 second.

• Therefore the duration of 1 tick is 1/50 = 0.02 seconds.



Pita Jangka Masa Detik

• Menunjukkan rekod gerakan troli.

• Jalur berdetik membuat 51 titik pada pita jangka masa detik setiap 1 saat.

• Sela masa antara dua titik dipanggil satu detik.

titik

1 detik

• Terdapat 50 titik pada pita jangka masa detik dalam masa 1 saat.

• Tempoh masa untuk setiap 1 titik ialah 1/50 = 0.02 saat.

The motion of an object can be deduced by studying the ticks formed on the ticker tape.

Analysis Of The Ticker Tape

Uniform but small

Uniform but big

Increasing in size

Decreasing in size



Type Of Motion

Gap between successive dots

low but uniform velocity.

high but uniform velocity.

velocity increases, object accelerating.

velocity decreases, object decelerating.

Type of motion Ticker tape

Jenis gerakan objek boleh ditakikkan dari jarak antara titik pada pita jangka masa detik.

Menganalisis Pita Jangka Masa Detik

Seragam dan jarak antara titik kecil

Seragam dan jarak antara titik besar

Jarak antara titik bertambah

Jarak antara titik berkurangan



Jenis Gerakan

Sela antara titik

Halaju perlahan dan seragam

Halaju tinggi dan seragam

Halaju bertambah, objek memecut

Halaju berkurangan, objek nyahpecut

Jenis gerakanPita jangka masa detik




Determining Average Velocity

The speed of the object pulling the ticker tape through the ticker timer can be determined as such

Average velocity = length of n ticks time for n ticks

Example8 cm

Number of ticks = 3length of 3 ticks = 8 cmtime for 3 ticks = (3)(0.02) = 0.06 s

Average velocity = (length of 3 ticks)/(time for 3 ticks) = 8 cm / 0.06 s = 133.33 cm s-1




Menentukan Purata Halaju

Purata halaju objek dapat ditentukan melalui:

Purata halaju = Panjang n titik

Masa bagi n titik

Contoh8 cm

Bilangan titik = 3Panjang 3 titik = 8 cmMasa bagi 3 titik = (3)(0.02) = 0.06 s

Purata halaju = (penjang 3 titik)/(masa bagi 3 titik) = 8 cm / 0.06 s = 133.33 cm s-1




Determining Acceleration

Initial velocity, u = 0.4cm / 0.02s = 20 cm/s

Final velocity , v = 2.4cm / 0.02s = 120 cm/s

Time = ( total number of ticks –1 ) x ( 0.02 )

= ( 11 – 1 ) x ( 0.02 )

= 10 0.02

= 0.2s

Acceleration, a = v – u t

a = 120 – 20 0.2

a = 100 / 0.2 = 500 cm s-2

0.4 cm 2.4 cm1

tick

2 tic

ks3

ticks

4 tic

ks

5 tic

ks

6 tic

ks

7 tic

ks

8 tic

ks

9 tic

ks

10 ti

cks

11 ti

cks




Menentukan Pecutan

Halaju awal , u = 0.4cm / 0.02s = 20 cm/s

Halaju akhir , v = 2.4cm / 0.02s = 120 cm/s

Masa = ( Jumlah bilangan titik –1 ) x ( 0.02 )

= ( 11 – 1 ) x ( 0.02 )

= 10 0.02

= 0.2s

Pecutan , a = v – u t

a = 120 – 20 0.2

a = 100 / 0.2 = 500 cm s-2

0.4 cm 2.4 cm1

titik

2 tit

ik3

titik

4 tit

ik

5 tit

ik

6 tit

ik

7 tit

ik

8 tit

ik

9 tit

ik

10 ti

tik11

titik

Characteristics Of Ticker Tape Chart - Uniform Velocity



The distance between successive dots are equally spaced.

All the ticker tapes are of the same length.

Time

Length (cm)

0

1

234

56

7

Ciri-ciri Carta Pita Jangka Masa Detik – Halaju Sekata



Jarak antara titik-titik adalah sama.

Keratan pita sama panjang

Masa

Panjang (cm)

0

1

234

56

7

Characteristics Of Ticker Tape Chart - Uniform Acceleration



Distance between successive dots increases uniformly.

Length of ticker tapes increases uniformly.

2.0

3.0

4.0

5.0

6.0

7.0Length / cm

Time

Ciri-ciri Carta Pita Jangka Masa Detik – Pecutan Seragam



Jarak antara titik bertambah secara seragam

Panjang keratan pita bertambah secara seragam

2.0

3.0

4.0

5.0

6.0

7.0Panjang / cm

Masa

Characteristics Of Ticker Tape Chart - Uniform Deceleration



Distance between successive dots decreases uniformly.

Length of ticker tapes decreases uniformly.

2.0

3.0

4.0

5.0

6.0

7.0Length / cm

Time

Ciri-ciri Carta Pita Jangka Masa Detik – Nyahpecutan Seragam



Jarak antara titik berkurangan secara seragam

Panjang pita berkurangan secara seragam

2.0

3.0

4.0

5.0

6.0

7.0Panjang / cm

Masa



Equations Of Linear Motion With Constant Acceleration

The three equations of linear motion with constant acceleration

v = u + at 2asuv 22 2at 21 +ut = s

where

u initial velocity =

v final velocity=

a acceleration=

t time=

s displacement=



Persamaan Gerakan Linear dengan Pecutan Seragam

Tiga persamaan gerakan linear dengan pecutan seragam

v = u + at 2asuv 22 2at 21 +ut = s

dimana

u Halaju awal=

v Halaju akhir=

a Pecutan=

t Masa=

s Sesaran=

Using the equation, v = u + at




Example 1

A car starts from rest, accelerates with a uniform acceleration of 3 ms -2. What will the velocity of the car after it had travelled for 10 seconds ?

initial velocity u = 0 ms-1 (since the car is at rest /stationary ) acceleration a = 3 ms-2 time taken t = 10 s

Solution :

final velocity v = ?

= 0 + (3)(10)

= 30 m s-1

The car will be moving at a velocity of 30 ms-1 after 10 seconds.

Menggunakan persamaan, v = u + at




Contoh 1

Sebuah kereta bergerak daripada keadaan rehat memecut dengan pecutan seragam 3 ms-2. Berapakah pecutan kereta itu selepas bergerak selama 10 saat?

Halaju awal u = 0 ms-1 (kereta dalam keadaan rehat sebelum bergerak) Pecutan a = 3 ms-2 Masa t = 10 s

Penyelesaian :

Halaju akhir v = ?

= 0 + (3)(10)

= 30 m s-1

Kereta itu bergerak pada halaju 30 ms-1 selepas 10 saat.




Example 2

A rocket being launched accelerates vertically upwards with a uniform acceleration of 50 ms-2.

How far is the rocket from the surface of the earth after 2 minutes of the launch?

initial velocity u = 0 ms-1 (rocket was stationary before launched)

acceleration a = 50 ms-2 time t = 2 60 = 120 s

Solution :

height from earth’s surface s = ?

2at 21 +ut = s 2(50)(120)

21 + (0)(120) =

= 360000 m= 360 km

Using the equation,




Contoh 2

Sebuah roket yang baru dilancarkan memecut secara menegak ke atas dengan pecutan seragam 50 ms-2.

Berapa jauhkah roket itu daripada permukaan Bumi selepas 2 minit dilancarkan?

Halaju awal u = 0 ms-1 (roket dalam keadaan rehat sebelum dilancarkan) Pecutan a = 50 ms-2

Masa t = 2 60 = 120 s

Penyelesaian :

Ketinggian daripada permukaan Bumi s = ?

2at 21 +ut = s 2(50)(120)

21 + (0)(120) =

= 360000 m= 360 km

Menggunakan persamaan,



2.2 2.2 Analysing Motion GraphsAnalysing Motion Graphs

Displacement – time graphs


Analysing Motion FraphsChapter 2 Forces and Motion

Can determine the displacement of an object at any time.

Can determine the time taken for an object to cover certain displacement.

Displacement / m

Time/s

75

60

45

30

15

10 20 30 40 50

At time t = 40 s, the displacement of object is 60 m.

The time taken for the object at the displacement 15 m is 10 s.

Example

To show the displacement of an object changes with time.

Graf sesaran - masa


Menganalisis Graf GerakanBab 2 Daya dan Gerakan

Boleh menentukan sesaran objek pada masa tertentu.

Boleh menentukan masa yang diambil oleh suatu objek untuk setiap sesaran.

Sesaran / m

Masa/s

75

60

45

30

15

10 20 30 40 50

Pada masa t = 40 s, sesaran objek ialah 60 m.

Masa yang diambil objek pada sesaran 15 m ialah 10 s.

Contoh

Menunjukkan sesaran objek berubah dengan masa.

Determining Velocity - Displacement-Time Graph


Analysing Motion GraphsChapter 2 Force And Motion

Displacement/m

Time/s

75

60

45

30

15

10 20 30 40 50

Example

velocity = gradient of displacement-time graph

velocity = gradient of displacement-time graph

velocity = 60 – 15

40 – 10

= 45 30

= 1.5 ms-1

Menentukan Halaju – Graf Sesaran - Mas



Sesaran/m

Masa/s

75

60

45

30

15

10 20 30 40 50

Contoh

Halaju = Kecerunan graf sesaran - masa

Halaju = kecerunan graf sesaran - masa

Halaju = 60 – 15

40 – 10

= 45 30

= 1.5 ms-1

Velocity-Time Graph



shows how the velocity of a moving object changes with time.

Velocity, v/ms-1

Time, t/s

25

20

15

10

5

1 2 3 4 50

30

Example

When time, t = 4 s, the velocity of the object is 20 ms-1

It takes 3 seconds for the object to achieve a velocity of 15 ms-1

Graf Halaju - Masa



Menunjukkan bagaimana halaju bagi objek bergerak berubah dengan masa.

Halaju, v/ms-1

Masa, t/s

25

20

15

10

5

1 2 3 4 50

30

Contoh

Pada masa, t = 4 s, halaju objek ialah 20 ms-1

Objek itu mengambil masa 3 saat untuk mencapai halaju 15 ms-1

Determining Acceleration - Velocity-Time Graph



Acceleration = gradient of the velocity-time graph

Acceleration = gradient of the velocity-time graph

Velocity, v/ms-1

Time, t/s

25

20

15

10

5

1 2 3 4 50

30

Example

acceleration = 20 – 0 4 – 0

= 204

= 5 ms-2

Menentukan Pecutan – Graf Halaju - Masa



Pecutan = kecerunan graf halaju - masa

Pecutan = kecerunan pada graf halaju - masa

Halaju, v/ms-1

Masa, t/s

25

20

15

10

5

1 2 3 4 50

30

Contoh

Pecutan = 20 – 0 4 – 0

= 204

= 5 ms-2

Determining Displacement - Velocity-Time Graph



The displacement of the object = area under the velocity-time graph

10

4 9

Velocity, v

Time, t/s

Displacement of the object from time, t = 4s to time, t = 9s, = area under the graph

= area of shaded region

(10)(5) 21 =

= 25 m

Example

Menentukan Sesaran – Graf Halaju - Masa



Sesaran objek = Luas di bawah graf halaju - masa

10

4 9

Halaju, v

Masa, t/s

Sesaran objek daripada masa, t = 4s hingga masa, t = 9s, = luas di bawah graf

= luas kawasan berlorek

(10)(5) 21 =

= 25 m

Contoh



Summary Of Motion Graphs

Gradient Velocity Acceleration

Area under the graph -------- Displacement

Displacement-time graph

Velocity-time graph



Ringkasan Graf Gerakan

Kecerunan Halaju Pecutan

Luas di bawah graf -------- Sesaran

Graf sesaran - masa Graf halaju - masa



2.3 2.3 Understanding InertiaUnderstanding Inertia

Observation

Explanation

Understanding Inertia

ITeach – Physics From 4

Inertia – Object At Rest

Inertia is a property of an object that causes it to resist any change to its state of motion.

Example

Chapter 2 Force And Motion

When the cardboard is flicked, the coin will drop into the glass.

An object that is at rest, will resist any effort to move it.

Coin at rest The coin’s inertia will resist any effort to move it.

Cardboard flicked The coin stays in its original position.

No cardboard

support

Gravity causes the coin to fall into the glass.

Pemerhatian

Penerangan

Memahami Inersia


Inersia – Objek dalam keadaan rehat

Inersia ialah kecenderungan objek menentang sebarang usaha untuk menggerakkannya daripada keadaan rehat.

Contoh

Bab 2 Daya dan Gerakan

Apabila kadbod ditarik, duit syiling akan jatuh ke dalam gelas.

Objek dalam keadaan rehat akan menentang sebarang usaha untuk menggerakkannya.

Syiling dalam keadaan rehat

Inersia syiling akan menentang sebarang usaha untuk menggerakkannya.

Kadbod ditarik Syiling kekal pada kedudukan asalnya.

Tanpa sokongan kadbod

Graviti menyebabkan syiling jatuh ke dalam gelas.

Observation

Explanation



Inertia –Object In Motion

Example

Chapter 2 Force And Motion

When the bus was moving

The passengers on the bus were also initially moving forward.

When the bus was stopped

The inertia of the passengers caused them to continue to move forward.

An object in motion will continue to move in a straight line unless acted upon by an external force.

When the bus stopped abruptly, the passengers were thrown forward.

Pemerhatian

Penerangan

Memahami Inersia


Inersia – Objek sedang bergerak

Contoh


Apabila bas sedang

bergerak

Penumpang juga bergerak ke hadapan.

Apabila bas berhenti

Inersia menyebabkan penumpang terus bergerak ke hadapan.

Objek yang sedang bergerak akan terus bergerak dalam satu garis lurus kecuali ditindakkan oleh daya luar.

Penumpang akan terhumban ke hadapan apabila bas yang sedang bergerak berhenti secara tiba-tiba.

Chapter 2 Forces and Motion



Inertia And Mass – Object At Rest

The inertia of an object depends on its mass.

An stationary object with a higher inertia is harder to be moved than an object with a lower inertia.

inertiaMass

Smaller mass

Empty trolley Trolley full of things

Hence it is easier to push an empty trolley.

Therefore lower inertia. Bigger mass

Hence it is harder to push a trolley full of things.

Therefore higher inertia.


Memahami Inersia


Inersia dan Jisim – Objek Dalam Keadaan Rehat

Inersia suatu objek bergantung kepada jisimnya.

Objek pegun dengan inersia yang tinggi adalah susah untuk digerakkan berbanding objek yang mempunyai inersia yang rendah.

InersiaJisim

Jisim kecil

Troli kosong Troli yang dipenuhi barang

Lebih mudah untuk menggerakkan troli kosong.

Inersia yang kurang Jisim yang besar

Lebih susah untuk menggerakkan troli yang dipenuhi barang.

Inersia yang lebih tinggi

Hence, it is more difficult to stop a moving aero-plane.




A moving object with a bigger mass is more difficult to stop than an object with a smaller mass.

Inertia And Mass – Object In Motion

Example

Smaller mass

Hence it is easier to stop a moving bicycle.

Therefore lower inertia.

Bicycle Aero-plane

Bigger mass Therefore higher inertia.

Lebih susah untuk menghentikan kapal terbang.


Memahami Inersia


Objek yang sedang bergerak dengan jisim yang besar adalah susah untuk diberhentikan berbanding objek yang mempunyai jisim yang kecil.

Inersia dan Jisim – Objek Sedang Bergerak

Contoh

Jisim kecil

Lebih mudah untuk menghentikan basikal.

Inersia rendah

Basikal Kapal terbang

Jisim yang lebih besar Inersia tinggi

Explanation

The hammer head and the handle moves when it is on its downward motion.

When handle touches the floor, the handle stops suddenly but the hammer head will continue to move downwards due to its inertia.

Hence the hammer head tightens.




The head of a hammer can be tightened by hitting the handle on the floor.

Positive Effects Of Inertia – Tightening A Hammer Head

Penerangan

Kepala penukul dan pemegangnya sedang bergerak apabila penukul dalam gerakan ke bawah.

Apabila pemegang menyentuh lantai, pemegang akan berhenti bergerak tetapi kepala penukul akan terus bergerak ke bawah disebabkan oleh inersia.

Maka, kepala penukul diketatkan.


Memahami Inersia


Kepala penukul boleh diketatkan dengan menghentak bahagian pemegangnya pada lantai.

Kesan Positif Inersia – Mengetatkan Kepala Penukul

Explanation

When the umbrella is being spun, the droplets on the umbrella is in a state of motion.

When the umbrella is stopped suddenly, the water droplets continues to move forward due its inertia and dislodge themselves form the umbrella.




Droplets of water dislodges themselves form a spinning umbrella when the umbrella is stopped abruptly.

Positive Effects Of Inertia – Drying An Umbrella

Penerangan

Titisan hujan pada payung dalam keadaan bergerak semasa payung berpusing.

Apabila payung berhenti berpusing secara tiba-tiba, titisan hujan akan terus bergerak ke hadapan disebabkan oleh inerisa dan titisan hujan keluar daripada payung.


Memahami Inersia


Titisan air hujan keluar dan jatuh daripada payung apabila payung yang sedang berpusing diberhentikan serta merta.

Kesan Positif Inersia – Mengeringkan Payung




Reducing The Negative Effects Of Inertia

When a car stops suddenly, the inertia of the passenger will cause him to move forward.

Seat Belt

The seat belt holds the passenger back, preventing the passenger form hitting the dashboard or the windscreen of the car.


Memahami Inersia


Mengurangkan Kesan Negatif Inersia

Apabila sebuah kereta berhenti dengan tiba-tiba, penumpang akan bergerak ke hadapan disebabkan oleh inersia.

Tali Pinggang

Tali pinggang mengelakkan penumpang terhumban ke hadapan.




Air Bag

The airbag is either mounted under the dashboard of in the steering wheel.

Reducing The Negative Effects Of Inertia – Air Bag

The air bag will inflate automatically in the event of an accident.

The airbag prevents the car passengers from colliding with the dashboard or the steering.


Memahami Inersia


Beg Udara

Beg udara diletakkan dibawah papan pemuka atau didalam stereng kereta.

Mengurangkan Kesan Negatif Inersia – Beg Udara

Beg udara akan mengembang secara automatik ketika kemalangan berlaku.

Beg udara menghalang penumpang daripada terhentak pada papan pemuka dan stereng kereta.


2.1 Arah Mata Angin


2.4 Analysing Momentum


Analysing Momentum

Definition Of Momentum

Momentum is defined as the product of the mass of an object and its velocity.


momentum = mass velocity = mv

Momentum is a vector quantity.

Momentum = mass velocity

= (2 kg)(4 ms-1)

= 8 kg ms-1

Momentum = mass velocity

= (4 kg)(- 2 ms-1)

= - 8 kg ms-1

4 ms-1

2 kg

2 ms-1

4 kg


Menganalisis Momentum

Definisi Momentum

Momentum ditakrifkan sebagai hasil darab jisim dengan halaju.


Momentum = Jisim Halaju = mv

Momentum ialah kuantiti vektor.

Momentum = jisim halaju

= (2 kg)(4 ms-1)

= 8 kg ms-1

Momentum = jisim halaju

= (4 kg)(- 2 ms-1)

= - 8 kg ms-1

4 ms-1

2 kg

2 ms-1

4 kg


Analysing Momentum


Principle Of Conservation Of Momentum

The total momentum of colliding objects before collision The total momentum after collision.=

The total momentum of colliding objects before collision is the same as the total momentum after collision.

= m1u1 + m2u2 m1v2 + m2v2




Prinsip Keabadian Momentum

Jumlah momentum sebelum pelanggaran

Jumlah momentum selepas pelanggaran=

Jumlah momentum objek-objek sebelum pelanggaran adalah sama dengan jumlah momentum selepas pelanggaran jika tiada

daya bertindak ke atas objek-objek yang berlanggar.

= m1u1 + m2u2 m1v2 + m2v2


Analysing Momentum


Momentum – Example

An object, P, of mass 4 kg moving with a velocity of 5 ms-1 collides with an object, Q, of mass 2 kg moving with a velocity of 1 ms-1 in the opposite direction.

If after the collision, object P moving with a velocity of 3 ms-1 in the same direction, determine the velocity of object Q after collision.

Solution

total momentum before collision = total momentum after collision mpup + mQuQ = mpvp + mQvQ

(4)(5) + (2)(-1) = (4)(3) + (2)(vQ)

20 – 2 = 12 + 2mQ

18 = 12 + 2mQ 2mQ = 6

mQ = 3 ms-1




Momentum – Contoh

Suatu objek, P, dengan jisim 4 kg sedang bergerak dengan halaju 5 ms -1 berlanggar dengan objek, Q, yang mempunyai jisim 2 kg dan bergerak dengan halaju1 ms-1 pada arah bertentangan.

Jika selepas pelanggaran, objek P bergerak dengan halaju 3 ms-1 pada arah yang sama, hitungkan halaju objek Q selepas pelanggaran.

Penyelesaian Jumlah momentum sebelum

pelanggaran = Jumlah momentum selepas

pelanggaran mpup + mQuQ = mpvp + mQvQ

(4)(5) + (2)(-1) = (4)(3) + (2)(vQ)

20 – 2 = 12 + 2mQ

18 = 12 + 2mQ 2mQ = 6

mQ = 3 ms-1

Before collision After collision

Characteristics

Objects moves separately after collision.

Total momentum is conserved.

Total kinetic energy is conserved.

Total energy is conserved.


Analysing Momentum


Elastic Collision

Sebelum pelanggaran Selepas pelanggaran

Ciri-ciri

Objek bergerak berasingan selepas pelanggaran.

Jumlah momentum diabadikan.

Jumlah tenaga kinetik diabadikan.

Jumlah tenaga diabadikan.




Pelanggaran Kenyal

Characteristics

Objects stick to each other and move with a common velocity after collision.

Total momentum is conserved.

Total kinetic energy after collision is less than total kinetic energy before collision.

Total energy is conserved.


Analysing Momentum


Before collision After collision

Inelastic Collision

Ciri-ciri

Objek bergerak bersama dengan halaju yang sama selepas pelanggaran.

Jumlah momentum diabadikan.

Jumlah tenaga kinetik selepas pelanggaran kurang daripada jumlah tenaga kinetik sebelum pelanggaran.

Jumlah tenaga diabadikan.




Sebelum pelanggaran Selepas pelanggaran

Pelanggaran Tak Kenyal

Applications Of Momentum


Analysing Momentum


Tennis

Soccer

The space shuttle lifting off

A boy jumps forward, boat moves backwards

Kegunaan Momentum




Tenis

Bola sepak

Roket bergerak ke atas

Seorang budak lompat dari sebuah bot ke hadapan,

bot bergerak ke belakang

Chapter 2 Forces And Chapter 2 Forces And MotionMotion

2.1 Arah Mata Angin


2.5 Understanding The Effect Of Force


Understanding The Effect Of ForceChapter 2 Forces And Motion

Force is a physical quantity that when acted on an object will cause the object to experience a change in

Effect Of Force

• Shape

• Size

• Speed

• Direction of motion of an object


Memahami Kesan DayaBab 2 Daya dan Gerakan

Daya ialah kuantiti fizik yang boleh mengubahkan keadaan pegun atau gerakan seragam suatu objek apabila daya bertindak ke atas suatu objek.

Kesan Daya

• Bentuk

• Saiz

• Laju

• Arah objek yang bergerak

Example 1:



Balanced Forces

When two of more forces acts on an object produces no nett force, then the forces are said to be balanced.

When balanced forces act on an object the object either

remains at rest moves with constant velocity

Example 2: Example 3:

Contoh 1:



Daya-daya yang Seimbang

Apabila dua atau lebih daya yang bertindak pada satu objek memusnahkan antara satu sama lain, daya paduan yang bertindak pada objek itu adalah seimbang.

Apabila daya-daya seimbang bertindak ke atas suatu objek,

objek itu akan

kekal dalam keadaan rehat Bergerak dalam kelajuan tetap

Contoh 2: Contoh 3:



When two or more forces acting on an object are not balanced,

Unbalanced Forces

Newton’s Second Law of motion

• The mathematical representation of Newton’s Second Law of Motion is

Fnet = ma

there will be a net force acting on the object.

the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.



Apabila dua atau lebih dari dua daya daya yang bertindak ke atas suatu objek adalah tidak seimbang

Daya-daya yang Tidak Seimbang

Hukum Gerakan Kedua Newton

• Hukum Gerakan Kedua Newton :

Fnet = ma

Daya paduan bukan sifar

Kadar perubahan momentum suatu objek adalah berkadar langsung dan dalam arah yang sama dengan daya paduan yang bertindak ke atasnya.



Example 1

20 N4 N

5 kg

Net force acting of object, Fnet = 20 + 4 = 24 N to the right

According to Newton’s Second Law of Motion,

24 = (5)a

Therefore acceleration, a = 24/5 = 4.8 ms-2

20 N 4 N5 kg

Fnet = 20 – 4 = 16 N to the right

According to Newton’s Second Law of Motion,

Fnet = ma

16 = (5)a

Therefore acceleration, a = 16/5 = 3.2 ms-2

Fnet = ma

Example 2



Contoh 1

20 N4 N

5 kg

Daya paduan pada obejk, Fnet = 20 + 4 = 24 N ke kanan

Mengikut Hukum Gerakan Kedua Newton

24 = (5)a

Pecutan, a = 24/5 = 4.8 ms-2

20 N 4 N5 kg

Fnet = 20 – 4 = 16 N ke kanan

Mengikut Hukum Gerakan Kedua Newton,

Fnet = ma

16 = (5)a

Pecutan, a = 16/5 = 3.2 ms-2

Fnet = ma

Contoh 2

There are 2 forces act on the system

• The man’s weight, W (downward)

• Normal reaction, R, act upward


Understanding The Effect of ForceChapter 2 Forces and Motion

A man standing on a weighing scale in a lift.

Lift

W

R

Application of Balanced and Unbalanced Forces

Situation 1 : The lift stays stationary or moving with constant velocity

Situation 2 : The lift accelerate upward with acceleration a.

Situation 3 : The lift accelerate downward with acceleration a.

Weighing machine

Lift

Terdapat 2 daya bertindak pada sistem

• Berat lelaki, W (ke bawah)

• Tindak balas normal, R, bertindak ke atas



Seorang lelaki berdiri di atas mesin penimbang di dalam sebuah lif.

Lif

W

R

Kegunaan Daya-daya Seimbang dan Tidak Seimbang

Situasi 1 : Lif pegun atau bergerak dengan halaju tetap.

Situasi 2 : Lif memecut ke atas dengan pecutan a.

Situasi 3 : Lif memecut ke bawah dengan pecutan a.

Mesin penimbang

Lif


2.1 Arah Mata Angin


2.6 Understanding Impulse And Impulsive Force


Analysing Momentum


Impulse

Impulse is defined as the change of momentum of an object, that isimpulse = final momentum – initial momentum

= mv - mu

impulse = final momentum – initial momentum

Example

= mv - mu

= (2)(4) – (2)(2) = 8 – 4

= 4 kg ms-1

2 kg

4 ms-1

2 kg

2 ms-1

before after2 kg

4 ms-1


Memahami Impuls dan Daya Impuls


Impuls

Impuls = Momentum akhir – Momentum awal= mv - mu

Impuls = Momentum akhir – Momentum awal

Contoh

= mv - mu

= (2)(4) – (2)(2) = 8 – 4

= 4 kg ms-1

2 kg

4 ms-1

2 kg

2 ms-1

sebelum selepas2 kg

4 ms-1

Impuls ditakrifkan sebagai perubahan momentum suatu objek.


Understanding Impulse And Impulsive ForceChapter 2 Forces And Motion

Impulsive Force

a strong force that acts within a short period of time between colliding objects.

Hitting nail with a hammer

Hitting a baseball with a baseball bat

Car involved in an accident

is defined as the rate of change of momentum in a collision :

Impulsive force , F = (mv – mu) ÷ t

Examples where impulsive force is produced


Memahami Impuls dan Daya ImpulsBab 2 Daya dan Gerakan

Daya Impuls

Suatu daya kuat yang bertindak dalam jangka masa pendek antara objek-objek yang berlanggar.

Memukul paku menggunakan

penukul

Memukul bola besbol dengan pemukul bola

besbol

Kereta terlibat dalam kemalangan

Ditakrifkan sebagai kadar perubahan momentum dalam pelanggaran :

Daya impuls , F = (mv – mu) ÷ t

Contoh-contoh daya impuls dihasilkan



Impulsive Force – Reducing The Impulsive Force

Large impulsive force may be harmful, therefore in certain situations impulsive force needs to be reduced.

Impulsive force can be reduced by increasing the time of impact between two colliding objects.



Daya Impuls – Mengurangkan Kesan Daya Impuls

Daya impuls yang besar adalah merbahaya, jadi daya impuls perlu dikurangkan dalam situasi yang tertentu.

Daya impuls boleh dikurangkan dengan memanjangkan masa pelanggaran antara objek-objek yang berlanggar.



High Jump – Reducing The Impulsive Force

• A mattress is placed at the landing area in a high jump event.

• When the high jumper lands on the mattress, the mattress compresses and increases the time taken for the high jumper to stop, thus increasing the time of impact and reducing the impulsive force.

• This will prevent serious injury on the high jumper .



Lompat Tinggi – Mengurangkan Kesan Daya Impuls

• Sebuah tilam diletakkan pada tempat mendarat dalam acara lompat tinggi

• Apabila atlet mendarat pada tilam, tilam akan mampat dan memanjangkan masa bagi atlet untuk berhenti, jadi masa yang panjang semasa hentaman dapat mengurangkan daya impuls.

• Ini dapat mengurangkan kecederaan atlet lompat tinggi.

• The bonnet of a car is soft and is able to crumple easily.

• When a collision occurs, the bonnet gets crumpled and this increases the time taken for the car to stop (increasing the time of impact) thereby reducing the impulsive force on the car.

• This will prevent the passengers of the car from suffering serious injuries.



Impulsive Force - Reducing The Impulsive Force

• Bonet kereta lembut dan mudah kemek.

• Apabila pelanggaran berlaku, bonet menjadi kemek dan ini memanjangkan msa untuk kereta berhenti (memanjangkan masa pelanggaran). Masa pelanggaran yang panjang dapat mengurangkan daya impuls pada kereta.

• Ini dapat menghalang penumpang kereta daripada mendapat kecederaan yang serius.



Daya Impuls – Mengurangkan Daya Impuls


2.1 Arah Mata Angin


2.7 Safety Features In Vehicles


Safety Features In VehiclesChapter 2 Forces And Motion

Safety features in cars are to reduce the damage to the cars and to reduce serious injuries to passengers caused by high impulsive force during collision.

Front bumper/Rear bumper : To absorb soft impact preventing damage to car

Front and rear crumple zones : Easily crushed to increase time of impact and hence decreases the magnitude of the impulsive force.Seat belt : Hold the passenger back preventing the passenger for being moving forward due to inertia

Importance Of Safety Features In A Car

Windscreen : Made of shatter-proof glass that will not break easily thus reducing injuries to passengers

Headrest : Prevents passengers from serious neck injuries.

Passenger safety case : Frame of car is reinforced to protect the passengers from injuries. Padded dashboard : Increases time of impact thus reducing impulsive force on passenger crashing onto the dashboard.

Steering wheel : Soft and easily crumpled, prevent driver from serious injuries to the head or chest during collision

Front bumperRear bumper

Front bumper/Rear bumper : To absorb soft impact preventing damage to carFront bumper/Rear bumper : To absorb soft impact preventing damage to car

Front and rear crumple zones : Easily crushed to increase time of impact and hence decreases the magnitude of the impulsive force.

Rear crumple zone

Front and rear crumple zones : Easily crushed to increase time of impact and hence decreases the magnitude of the impulsive force.

Seat belt

Windscreen

Headrests

Seat belt : Hold the passenger back preventing the passenger for being moving forward due to inertia

Seat belt : Hold the passenger back preventing the passenger for being moving forward due to inertia



Headrest : Prevents passengers from serious neck injuries. Headrest : Prevents passengers from serious neck injuries.

Passenger safety case

Padded dashboard

Steering wheel

Passenger safety case : Frame of car is reinforced to protect the passengers inside from injuries.

Passenger safety case : Frame of car is reinforced to protect the passengers from injuries.

Padded dashboard : Increases time of impact thus reducing impulsive force on passenger crashing onto the dashboard.

Padded dashboard : Increases time of impact thus reducing impulsive force on passenger crashing onto the dashboard.



Front crumple zone


Ciri Keselamatan dalam KeretaBab 2 Daya dan Gerakan

Ciri keselamatan dalam kereta dapat mengurangkan kerosakan kereta dan mengelakkan kecederaan yang serius pada penumpang yang disebabkan oleh daya impuls semasa pelanggaran.

Bamper depan/belakang : Untuk menyerap hentaman dan menghalang kerosakan kereta

Zon remuk depan dan belakang : Mudah remuk untuk memanjangkan masa pelanggaran dan mengurangkan daya impuls

Tali pinggang : Memegang penumpang supaya penumpang tidak terhumban ke hadapan disebabkan inersia.

Kepentingan Ciri Keselamatan dalam Kereta

Cermin depan: Dibuat daripada kaca tidak berkecai yang akan mengurangkan kecederaan penumpang.

Penahan kepala: Menghalang penumpang daripada kecederaan di leher.

Sarung keselamatan penumpang : Bingkai kereta dibuat dengan kukuh untuk melindungi penumpang daripada kecederaan.Pad papan pemuka : Meningkatkan masa hentaman dan mengurangkan daya impuls pada penumpang.

Stereng kereta : Lembut dan mudah remuk, menghalang pemandu daripada mendapat kecederaan yang serius pada kepala atau dada.

Bamper hadapanBamper belakang

Bamper depan/belakang : Untuk menyerap hentaman dan menghalang kerosakan keretaBamper depan/belakang : Untuk menyerap hentaman dan menghalang kerosakan keretaZon remuk depan dan belakang : Mudah

remuk untuk memanjangkan masa pelanggaran dan mengurangkan daya impuls

Zon remuk belakang

Zon remuk depan dan belakang : Mudah remuk untuk memanjangkan masa pelanggaran dan mengurangkan daya impuls

Tali pinggang

Cermin depan

Penahan kepala

Tali pinggang : Memegang penumpang supaya penumpang tidak terhumban ke hadapan disebabkan inersia.Tali pinggang : Memegang penumpang supaya penumpang tidak terhumban ke hadapan disebabkan inersia.





Sarung keselamatan penumpang

Pad papan pemuka

Stereng kereta

Sarung keselamatan penumpang : Bingkai kereta dibuat dengan kukuh untuk melindungi penumpang daripada kecederaan.

Sarung keselamatan penumpang : Bingkai kereta dibuat dengan kukuh untuk melindungi penumpang daripada kecederaan.

Pad papan pemuka : Meningkatkan masa hentaman dan mengurangkan daya impuls pada penumpang.

Pad papan pemuka : Meningkatkan masa hentaman dan mengurangkan daya impuls pada penumpang.Stereng kereta : Lembut dan mudah remuk, menghalang pemandu daripada mendapat kecederaan yang serius pada kepala atau dada.

Stereng kereta : Lembut dan mudah remuk, menghalang pemandu daripada mendapat kecederaan yang serius pada kepala atau dada.

Zon remuk hadapan


2.1 Arah Mata Angin


2.8 Understanding Gravity


Understanding gravityChapter 2 Forces And Motion

Acceleration Due To Gravity

All objects are able stay on the surface of the Earth or fall to the ground due to the gravitational force that pulls them towards the centre of the Earth.

Coconut falling from a coconut tree

Satellite orbiting the earthAble to stay on the surface of the earth

ITeach – FiziK Tingkatan 4

Memahami GravitiBab 2 Daya dan Gerakan

Graviti

Semua objek dapat berdiri tegak di permukaan Bumi atau jatuh ke tanah disebabkan oleh daya graviti yang menarik semua objek ke pusat Bumi.

Buah kelapa jatuh dari pokok kelapa

Satellit mengorbit BumiManusia dapat berdiri di permukaan Bumi



Gravitational pull of the earth causes an object to accelerate at a constant rate as it falls.

The acceleration is known as the acceleration due to gravity, represented by the symbol ‘g’.

The acceleration due to gravity of the earth, g = 9.81 ms-2 (~ 10 ms-2).This means that the speed of a falling object increases by 10 ms-1 every 1 second as it falls to the surface of the earth.

Acceleration Due To Gravity

0 m/s → 0 s 10 m/s → 1 s 20 m/s → 2 s

30 m/s → 3 s

40 m/s → 4 s

50 m/s → 5 s



Tarikan daya graviti menyebabkan objek memecut pada kadar malar ketika objek bergerak jatuh ke tanah.

Pecutan ini dikenali sebagai pecutan graviti , diwakili oleh simbol ‘g’.

Pecutan graviti, g = 9.81 ms-2 (~ 10 ms-2). Laju bagi objek yang sedang jatuh ke permukaan Bumi meningkat sebanyak 10 ms-1 setiap 1 saat.

Pecutan Disebabkan Oleh Graviti

0 m/s → 0 s 10 m/s → 1 s 20 m/s → 2 s

30 m/s → 3 s

40 m/s → 4 s

50 m/s → 5 s



Weight

Weight of an object is defined as the gravitational force that acts on the object.

Weight, W = mass × acceleration due to gravity = mg

Example

Note : To calculate the weight of an object, the mass must be measured in kilogram while the acceleration due to gravity in units of ms-2

• A boy of mass 55 kg have a weight of (55)(10) = 550 Newton

• The weight of a 60 gram pencil is (60/1000)×(10) = 0.6 Newton

Note : The acceleration due to gravity on the surface of the moon is 1/6 the acceleration due to gravity on the surface of the earth

The acceleration due to gravity on the moon is about 1.66 ms-2



Berat

Berat ialah daya yang bertindak ke atas jisim sesuatu objek oleh tarikan Bumi.

Berat, W = Jisim × Pecutan graviti = mg

Contoh

Nota : Untuk mengira berat sesuatu objek, jisim mesti dikira dalam kilogram dan pecutan graviti dalam unit ms-2

• Seorang budak dengan jisim 55 kg mempunyai berat (55)(10) = 550 Newton

• Berat bagi 60 gram pensel ialah (60/1000)×(10) = 0.6 Newton

Nota : Pecutan graviti pada permukaan bulan adalah 1/6 daripada pecutan graviti di permukaan Bumi.

Pecutan graviti di permukaan Bulan ialah 1.66 ms-2



The Differences Between Mass And Weight

Mass, m Weight, W

The amount of matter in an object The gravitational force acting on an object

Base quantity Derived quantity

S I Unit : kilogram S I Unit : Newton

Value is constant everywhere. Value depends on the acceleration due to gravity.

Scalar quantity Vector quantity

Example

An object of mass 10kg on earth also has a mass of 10kg on the moon.

Example

An object weights 600 N on earth will only weigh 100N on the moon.



Perbezaan Antara Jisim Dengan Berat

Jisim, m Berat, W

Jumlah jirim yang ada dalam sesuatuobjek

Daya yang bertindak ke atas sesuatu objek

Kuantiti asas Kuantiti terbitan

S I Unit : kilogram S I Unit : Newton

Nilai tetap Nilai bergantung kepada pecutan graviti.

Kuantiti skalar Kuantiti vektor

Contoh

Jisim suatu objek di Bumi ialah 10 kg. Jisim objek itu di Bulan juga adalah 10 kg.

Contoh

Berat suatu objek di Bumi ialah 600 N. Berat objek itu di Bulan ialah 100 N.


2.1 Arah Mata Angin


2.9 Analysing Forces In Equilibrium


Analysing Forces In EquilibriumChapter 2 Forces And Motion

When the forces acting on an object is in equilibrium, then no net (resultant) force acts on the object.

Forces In Equilibrium

Example

A pile book on a tableA rifle hanging on a wall

A car moving with constant velocity An object resting on an inclined plane

The object will either be at rest (stationary) or moves with constant velocity.


Menganalisis Daya - daya KeseimbanganBab 2 Daya dan Gerakan

Apabila daya-daya yang bertindak pada suatu objek adalah seimbang, maka tiada daya paduan bertindak pada objek itu.

Daya – daya Keseimbangan

Contoh

Buku-buku yang bertindih di atas mejaSenapang digantung pada dindingl

Kereta bergerak dengan halaju seragam Suatu objek dalam keadaan rehat pada satah condong

Objek itu akan berada pada keadaan rehat (pegun) atau bergerak pada halaju tetap.



Two parallel forces are in equilibrium if the two forces have the same magnitude but act in opposite directions.

Forces In Equilibrium – Parallel Forces

Examples

T F

F

T

drag

forward thrust

A car moving with constant velocity

driving force frictional forces

The driving force and the frictional force are in equilibrium

An aeroplane cruising at constant velocity

Forward thrust and drag are in equilibrium


Menganalisis Daya – daya KeseimbanganBab 2 Daya dan Gerakan

Dua daya-daya selari adalah seimbang jika kedua-dua daya mempunyai magnitud yang sama tetapi bertindak pada arah yang berlainan.

Daya – daya Keseimbangan – Daya – daya Selari

Contoh

T F

F

T

seretan

Tujahan ke hadapan

Sebuah kerera bergerak dengan halaju seragam

Daya memandu

Daya geseran

Daya memandu dan daya geseran dalam keadaan seimbang

Sebuah kapal terbang bergerak pada halaju seragam

Tujahan ke hadapan dan seretan berada dalam keadaan seimbang

The diagram below shows three forces P, Q and R acting in a system.The three forces are in equilibrium.



Forces In Equilibrium - Three Non-Parallel Forces

wallwallR

QP

90°

30°

30°

P

RQ

A closed triangle will be obtained if the three forces are drawn end-to-end

Rajah di bawah menunjukkan tiga daya P, Q dan R bertindak pada satu sistem. Ketiga – tiga daya berada dalam keadaan seimbang.


Menganalisis Daya – daya KeseimbanganBab 2 Daya dan Gerakan

Daya – daya Keseimbangan – Tiga Daya- daya Tidak Selari

DindingDindingR

QP

90°

30°

30°

P

RQ

Sebuah segitiga akan diperolehi jika garisan pada ketiga-tiga daya disambungkan



Resultant Force – Parallelogram Of Forces

When two force P and Q acts on a object, the resultant force F, is represented by the diagonal of a parallelogram drawn using the forces P and Q.

Example : The resultant of the forces P and Q can be obtained as shown

If drawn to scale, the length of the diagonal OC represents the magnitude of the resultant force while the angle shows the direction of the resultant force.

PA0

0P

Q

B

0P

B C

QQ

P

0P

PB C

QQ

Aθ


Menganalisis Daya-daya KeseimbanganBab 2 Daya dan Gerakan

Hasil Campur Daya-daya – Segiempat Selari

Apabila dua daya P dan Q bertindak pada suatu objek, hasil campur daya F, diwakili pepenjuru segiempat selari.

Contoh : Hasil campur daya-daya P dan Q boleh diperolehi seperti dibawah:

Jika dilukis mengikut skala, panjang pepenjuru OC mewakili magnitud hasil campur daya-daya manakala sudut menunjukkan arah hasil campur daya-daya.

PA0

0P

Q

B

0P

B C

QQ

P

0P

PB C

QQ

Aθ

Resolution Of Forces



A force can be resolved into two components, that is, the two components, that is, the

horizontal component, Fx, and the

Vertical component, Fy

θFx = F cosθ

Fy = F sinθF

Leraian Daya



Satu daya boleh dileraikan kepada 2 komponen iaitu

Komponen ufuk, Fx, dan

Komponen tegak, Fy

θFx = F cosθ

Fy = F sinθF

The force that moves the boat horizontally is the horizontal component of the force F = 500N



Resolution Of Forces – Horizontal Component

The horizontal component, Fx, is the “effective” force that moves the object in the horizontal direction.

Example

That is, Fx = F cos 15° = (550)(0.9659) = 531.3N

boat

river

ropeF = 550 N,

15°

Daya yang menggerakkan bot secara mengufuk adalah komponen ufuk daya F = 500N



Leraian Daya – Komponen Ufuk

Komponen ufuk, Fx, adalah daya yang menggerakkan objek pada arah mengufuk.

Contoh

Fx = F cos 15° = (550)(0.9659) = 531.3N

bot

sungai

taliF = 550 N,

15°


2.1 Arah Mata Angin


2.10 Understanding Work, Energy, Power And Efficiency


Understanding Work, Energy, Power And EfficiencyChapter 2 Forces And Motion

Work Done

Work is a kind of energy transfer.

Work is done if an object acted upon by a force moves in the direction of the force.

Work done, W = applied force, F × distance moved in the direction of the applied force, s

Therefore work done, W =

F F

s

Fs

ITeach – Fizik Tingkatab 4

Memahami Kerja, Tenaga, Kuasa dan KecekapanBab 2 Daya dan Gerakan

Kerja Dilakukan

Kerja ialah satu jenis pemindahan tenaga.

Kerja dilakukan jika suatu objek bertindak melalui daya dan bergerak pada arah daya.

Kerja dilakukan, W = Daya, F × sesaran dalam arah daya itu, s

Kerja dilakukan, W =

F F

s

F s



Work Done

If the applied force makes an angle with the direction of motion of the object, as shown

work done,W = horizontal component of the force × displacement

work done, W = (F cos) (s)

= Fs cos

The unit of work is Newton meter (N m) of Joule (J)

θ θ

F F

s



Kerja Dilakukan

Jika daya dikenakan membuat sudut pada arah objek bergerak, seperti dibawah:

Kerja dilakukan,W = Komponen ufuk daya × Sesaran

Kerja dilakukan, W = (F kos ) (s)

= Fs kos

Unit kerja ialah Newton meter (N m) atau joule (J)

θ θ

F F

s



Examples Of Work Done

Pushing a shopping cart

Car barking. Work is done by the brakes.

Weightlifting



Contoh Kerja Dilakukan

Menolak troli Kereta membrek. Kerja dilakukan oleh brek.

Angkat berat



The object that is acted upon by a force remains stationary.

The direction of motion of the object is perpendicular to the applied force.

Examples Of Work Not Done

Man pushing a wall

Waiter walking towards the diner



Objek yang ditindakkan oleh suatu kekal berada dalam keadaan pegun.

Arah pergerakan objek berserenjang dengan daya yang dikenakan.

Contoh Kerja Tidak Dilakukan

Seorang lelaki menolak dinding

Pelayan berjalan ke arah meja



Energy

Energy is the ability of an object to do work.

When work is done on an object, the object gains energy.



Tenaga

Tenaga ialah keupayaan sesuatu objek untuk melakukan kerja.

Apabila kerja dilakukan pada suatu objek, objek mendapat tenaga.



Kinetic Energy

Kinetic energy is the energy possesses by an object because of its motion.

This means that any object that moves have kinetic energy.

The magnitude of the kinetic energy possessed by an object of mass m kilogram moving with a speed of v meters per second is

Examples a moving car

A bowling ball rolling towards the bowling pins

An electron orbiting an atom

Kinetic energy = ½ m v2



Tenaga Kinetik

Tenaga kinetik ialah tenaga yang disebabakan oleh gerakan.

Sebarang objek yang bergerak mempunyai tenaga kinetik.

Tenaga kinetik bagi suatu objek dengan jisim m kilogram dan bergerak dengan laju v meter per saat diberi oleh formula

Contoh Kereta yang sedang bergerak

Bola boling bergerak ke arah lorong boling

Elektron mengorbit atom

Tenaga Kinetik = ½ m v2



Gravitational Potential Energy

Potential energy is energy that is stored in an object

When work is done in lifting the box to a certain height above the ground, the box gains gravitational potential energy.The gravitational potential energy of an object depends on its mass and its height above the ground. Gravitational potential energy = mgh

g = acceleration due to gravity Where m = mass

h = vertical height of object above the ground

force

displacement

Work is done



Tenaga Keupayaan Graviti

Tenaga keupayaan ialah tenaga yang diperoleh oleh suatu objek yang disebabkan oleh ketinggiannya dalam medan graviti.

Kotak mendapat tenaga keupayaan graviti apabila kerja mengangkat kotak dilakukan hingga ke satu aras ketinggian di atas permukaan Bumi.Tenaga keupayaan graviti bergantung kepada jisim dan ketinggian di atas permukaan Bumi.Tenaga keupayaan graviti = mgh

g = pecutan disebabkan oleh gravitiDimana m = jisim

h =ketinggian objek di atas permukaan Bumi

Daya

Sesaran

Kerja dilakukan

The stretched rubber band of the catapult stores energy



Elastic Potential Energy

Elastic potential energy is the energy stored in an elastic object that is compressed or stretched.

A compressed spring stores energy

Gelang getah yang diregangkan mempunyai tenaga keupayaan kenyal



Tenaga Keupayaan Kenyal

Tenaga keupayaan kenyal ialah tenaga yang tersimpan dalam suatu bahan kenyal yang di dimampatkan atau diregangkan.

Spring yang dimampatkan mempunyai tenaga keupayaan kenyal



Other Common Forms Of Energy

Chemical energy in a dry cell

Heat energy

Light energy

Electrical energy

Sound energy



Bentuk Tenaga yang Lain

Tenaga kimia pada sel kering

Tenaga haba

Tenaga cahaya

Tenaga elektrik

Tenaga bunyi



Examples:

Chemical energy to light heat

Gravitational potential energy to kinetic energy

Gravitational potential energy to electrical energy

Principle Of Conservation Of Energy

The amount of energy in the universe is constant.

Energy cannot be created nor it can be destroyed.

The Principle of Conservation of Energy states that energy can neither be created nor destroyed but energy changes from one form to another.


Memahami Kerja, Tenaga, Kuasa dan KecekapanKuasa 2 Daya dan Gerakan

Contoh :

Tenaga kimia ke tenaga haba

Tenaga keupayaan graviti kepada tenaga kinetik

Tenaga keupayaan graviti kepada tenaga elektrik

Prinsip Keabadian Tenaga

Jumlah tenaga di alam semesta adalah tetap.

Tenaga tidak boleh dicipta atau dimusnahkan.

Prinsip Keabadian Tenaga menyatakan tenaga boleh berubah daripada satu bentuk ke bentuk lain tetapi tenaga tidak boleh dicipta atau dimusnahkan.



Power

Power, P, is the rate at which work is done or energy is transferred.

Power, P =Work done, W or Energy, E

Time taken,t

Power, P = E/t

The unit of power is Joule per second (Js-1) or the Watt (W)

Example : An electric bulb rated 50 W used 50 Joules of electrical energy per second



Kuasa

Kuasa, P, ialah kadar kerja dilakukan atau pemindahan tenaga.

Kuasa, P =Kerja dilakukan, W atau Tenaga, E

Masa diambil,t

Kuasa, P = E/t

Unit bagi kuasa ialah Joule per saat (Js-1) atau Watt (W)

Contoh : Sebiji mentol elektrik pada kadar 50 W menggunakan 50 joule tenaga elektrik setiap satu saat.



2.11 2.11 Understanding ElasticityUnderstanding Elasticity


Understanding ElasticityChapter 2 Force And Motion

ElasticityAn object is said to be elastic if the object returns to its original shape when the force

acting on it is removed.

Example

Spring Elastic Band


Memahami KekenyalanBab 2 Daya dan Gerakan

KekenyalanSuatu objek dikatakan kenyal jika objek itu kembali ke bentuk asal apabila daya yang

bertindak ke atas objek dialihkan.

Contoh

Spring Gelang getah

Spring mendapat tenaga keupayaan kenyal apabila ditekan atau diregang

pegun

dimampat diregang

Tenaga keupayaan kenyal



Hooke’s Law

Hooke’s Law states that the extension of a spring is directly proportional to the stretching force that acts on it provided the elastic limit is not exceeded.

The elastic limit is the maximum force that can be applied to the spring before it ceases to be elastic.

metre rule

retort stand

load



Hukum Hooke

Hukum Hooke menyatakan pemanjangan spring adalah berkadar terus dengan daya yang dikenakan dengan syarat daya yang dikenakan tidak melebihi had kenyal.

Had kenyal ialah daya pemanjangan maksimum yang boleh dikenakan ke atas spring sebelum spring menjadi tidak kenyal dan pemanjangannya menjadi kekal.

Pembaris meter

Kaki retort

Beban

Beyond E (E to P)Elastic limit is exceeded. If the stretching force is removed, the spring suffers permanent damage and will be deformed.

Point E : elastic limit



Hooke’s Law - Graph of applied force against extension

The graph of the stretching force against the extension produced by a spring

Line OE : Hooke’s law is obeyed. If the stretching force is removed, the spring will return to its original length.

PE

F

OX

F = kxspring obeyingHooke’s law spring not

obeying Hooke’s law

Melebihi E (E hingga P)Melebihi had limit. Jika daya yang dikenakan dialih, pemanjangan spring akan kekal dan spring akan rosak.

Titik E : Had kenyal



Hukum Hooke - Graf Daya yang Dikenakan Melawan Daya Pemanjangan

Graf daya yang dikenakan melawan pemanjangan spring dihasilkan oleh spring

Garis OE : Hukum Hooke tidak dipatuhi. Jika daya yang dikenakan dialihkan, spring akan kembali ke panjang asal.

PE

F

OX

F = kxspring mematuhiHukum Hooke Spring tidak

mematuhi Hukum Hooke



Hooke’s Law - The elastic constant or spring constant

• When Hooke’s Law is obeyed, the graph of applied force against extension is a straight line through the origin.

• Hooke’s Law states that F = kx where k is the spring constant.

• The gradient of the F-x graph gives the spring constant of the spring.

• The higher the spring constant, the stiffer (less elastic) is the spring and vice versa.



Hukum Hooke - Pemalar spring

• Apabila hukum Hooke dipatuhi, graf daya yang dikenakan melawan pemanjangan spring adalah suatu graf garis lurus.

• Hukum Hooke menyatakan F = kx dimana k ialah pemalar spring.

• Kecerunan graf F-x memberi nilai pemalar spring.

• Semakin tinggi nilai pemalar spring, semakin tegang (kurang kenyal) spring dan sebaliknya.

Daya, F / N

Pemanjangan spring, x / cm



Length Short Long

F F

Diameter of spring coil Large diameter Small diameter

FF

Factors Stiff Less Stiff

Diameter of material of spring

Thin wire Thick wire

F F

Material used as spring

F F

copper spring

Steel spring

Arrangement of springs

Parallel Series

mm

Factors Affecting The Elasticity Of A Spring

PanjangDiameterkecilDawai tebalBersiriPendekDiameter

besarDawai nipisSelari Susunan springPanjangDiameter gegelung

springDiameter bahan springBahan yang digunakan

sebagai spring



F FFF

Faktor Tegang Kurang tegang

F FF F

Springkuprum

Spring besi

mm

Faktor yang Mempengaruhi Kekenyalan Spring



Elastic Potential Energy

A stretched spring stores energy as elastic potential energy.

elastic potential energy stored in a spring.F / N

x / mo

area under the Force against extension graph.

=

2e kx

21Fx

21E



Tenaga Keupayaan

Kenyal Spring yang diregangkan menyimpan tenaga

sebagai tenaga keupayaan kenyal.

Tenaga keupayaan kenyal tersimpan dalam springF / N

x / mo

Luas dibawah graf daya melawan pemanjangan

spring.

=

2e kx

21Fx

21E



Application Of Elasticity

Spring Mattress Shock absorber Spring balance Ammeter



Aplikasi Kekenyalan

Tilam spring Penyerap kejutan Penimbang spring Ammeter

The End

i - Teach

Chapter 2 Forces and Motion

Documents

Transcript of Chapter 2 Forces and Motion