Post on 25-May-2015
1.3 1.3 Understanding Scalar & Understanding Scalar &
Vector QuantitiesVector Quantities
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1.3 1.3 Understanding Scalar & Vector Understanding Scalar & Vector
QuantitiesQuantities
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Chapter 1 Chapter 1 Introduction To PhysicsIntroduction To Physics
Learning OutcomesLearning Outcomes
DefineDefine scalar and vector scalar and vector quantitiesquantities
Give examplesGive examples of scalar and of scalar and vector quantitiesvector quantities
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Physical QuantitiesPhysical Quantities
MagnitudeMagnitudenono directiondirection
MagnitudeMagnitudedirectiondirection
vector vector ScalarScalar
Displacement, Displacement, velocity, force, velocity, force, Acceleration, Acceleration, Momentum, weight, Momentum, weight, impulse, pressureimpulse, pressure
Length, mass, time Length, mass, time electric current, electric current, temperature, area, temperature, area, distance, speed, distance, speed, energy,density,powerenergy,density,power
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Conduct simple activity (pg 10)Conduct simple activity (pg 10)
Physics Lab PlanPhysics Lab Plan
8 m
14 m
O C
BA
16 m
Idea : Idea : distance & displacement ; distance & displacement ; speed & velocityspeed & velocity
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Distance = total length of the Distance = total length of the path travelledpath travelled
Displacement = distance Displacement = distance travelled from its initial position travelled from its initial position to its final positionto its final position
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Total Total distancdistance, s/me, s/m
Displacement, Displacement, d/md/m
time, time, t/st/s
speed/ speed/ m sm s-1-1
velocity/ velocity/ m sm s-1-1
AA 88 8 from O to A8 from O to A 2.402.40 3.333.33 3.33 3.33 from O from O to Ato A
BB 2222 16 from O to B16 from O to B 5.285.28 4.174.17 3.033.03
CC 3030 14 from O to 14 from O to CC
7.657.65 3.923.92 1.831.83
OO 4444 0 from O to O0 from O to O 10.3210.32 4.264.26 0.000.00
Displacement = Displacement = distance travelled from its initial position to its final position
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Total Total distancdistance, s/me, s/m
Displacement, Displacement, d/md/m
time, time, t/st/s
speed/ speed/ m sm s-1-1
velocity/ velocity/ m sm s-1-1
AA 88 ___ from O to ___ from O to AA
7.517.51 1.071.07 1.07 1.07 from O from O to Ato A
BB 2222 ___ from O to ___ from O to BB
15.5115.51 1.421.42 1.031.03
CC 3030 ___ from O to ___ from O to CC
22.0522.05 1.361.36 0.630.63
OO 4444 ___ from O to ___ from O to OO
25.5025.50 1.731.73 0.000.00
Displacement = Displacement = distance travelled from its initial position to its final position
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Total Total distancedistance, s/m, s/m
DisplacementDisplacement, d/m, d/m
time, time, t/st/s
speed/ speed/ m sm s-1-1
velocity/ velocity/ m sm s-1-1
AA 9.09.0 9 from O to 9 from O to AA
3.133.13 2.872.87 2.87 2.87 from O from O to Ato A
BB 15.515.5 11.1 from O 11.1 from O to Bto B
5.345.34 2.902.90 2.08 2.08 from O from O to Bto B
CC 24.524.5 6.5 from O to 6.5 from O to CC
8.248.24 2.972.97 0.79 0.79 from O from O to Cto C
OO 31.031.0 0 from O to O0 from O to O 10.6710.67 2.902.90 0.00 0.00 from O from O to Oto Owww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
Scalar Scalar QuantitiesQuantities
Vector Vector QuantitiesQuantities
e.g: distance, e.g: distance, speedspeed
Displacement Displacement , velocity, velocity
Has Has magnitude but magnitude but no direction no direction
Has Has magnitude magnitude and direction and direction
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Addition Scalar & Addition Scalar & Vector Quantities Vector Quantities
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Adding Scalar QuantityAdding Scalar Quantity
Can be added, subtracted, multiplied and divided like ordinary numbers. e.g: (a) 3 kg of sand is added to 1 kg cement, resulting mixture has a mass of 4 kg(b) 5 liters of water are poured from a pail that has 8 liters of water in it.
The resulting volume is 3 litersNo direction is involved!
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Scalar QuantitiesScalar Quantities
5 kg5 kg 10 kg 10 kg
Total mass Total mass = 5 + 10= 5 + 10 = 15 kg= 15 kg
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Adding Vector QuantityAdding Vector Quantity
An arrow is used to represent the magnitude and direction of a vector quantity.
Same direction = sumOpposite direction = minus
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eg. 1eg. 1
50 N50 N 30 N 30 N
Total ForceTotal Force* * = 50 + 30= 50 + 30= 80 N = 80 N (80 N due west//to the left)(80 N due west//to the left)
*=*=resultant forceresultant force////net forcenet forcewww.myfunphysicsworld.blogspot.comwww.myfunphysicsworld.blogspot.com
50 N50 N 10 N 10 N
Total Force Total Force = 50 - 10= 50 - 10
= 40 N = 40 N
(40 N due west//to the left)(40 N due west//to the left)
eg. 2eg. 2
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50 N50 N 50 N 50 N
Total Force Total Force = = 50 - 5050 - 50
= = 0 N 0 N
(object is (object is not movingnot moving////at restat rest////stationarystationary))
eg. 3eg. 3
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How much is the resultant How much is the resultant force?force?
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Adding Vector QuantityAdding Vector QuantityAn arrow is used to represent the magnitude and direction of a vector quantity.
e.g :
velocity of airplane = 100 km/h
wind velocity = 20 km/h
(a) If same direction,
Resulting velocity of airplane= 100 + 20 = 120 km/h
(a) If opposite direction,
resulting velocity of airplane = 100 -20 = 80 km/h
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Special Case: Special Case: Non-parallel vectorsNon-parallel vectors
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Two vectors acting at a point can be replaced Two vectors acting at a point can be replaced by a single vector with the same effect.by a single vector with the same effect.
Case 1Case 1
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Case 2Case 2
Two vectors acting at a point can be replaced Two vectors acting at a point can be replaced by a single vector with the same effect.by a single vector with the same effect.
Resultant Vector
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Homework Homework
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1. Jeremy walked 3 m due east, and then 1. Jeremy walked 3 m due east, and then 4 m due north.4 m due north.
(a) What is his total distance?(a) What is his total distance?
3 m + 4 m = 7 m3 m + 4 m = 7 m
(b) What is his displacement?(b) What is his displacement?
5 m5 m
3 m
5 m4 m
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2. Every morning Amirul walks to Badrul’s 2. Every morning Amirul walks to Badrul’s house which is situated 80m to the east house which is situated 80m to the east of Amirul’s house. of Amirul’s house.
They then walks towards their school They then walks towards their school which is 60m to the south of Badrul’s which is 60m to the south of Badrul’s house.house.
What is the distance traveled by Amirul What is the distance traveled by Amirul and his displacement from his house?and his displacement from his house?
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