Mindmap nat5ppt

Nuclear radiation

WavesWaves Dynamics

EnergySpace

National 5 Revision

Kinross High School

WAVESWAVES

Types of waves:Longitudinal (e.g. sound) - the direction of vibration is the same as the direction of the wave.Transverse (e.g. light) - the direction of vibration is at right angles to the direction of the wave.

The wave equation:speed = frequency x wavelength

speed, v, in m/sfrequency. f. in Hzwavelength, lambda, in m.

Definitions:Frequency - the number of waves produced (or pass a point) each second.Speed - the distance a wave travels in one second. Wavelength - the distance between two neighbouring crests (or troughs) / distance from one point on a wave to the same point on the next wave.Amplitude - the height of the wave, from the centre position to the crest (or trough)Period - the time taken to produce one complete wave / the time taken for one wave to pass a point.

Speed, distance and time:speed = distance / time; time is always in seconds.

Electromagnetic spectrum:(in order of increasing wavelength/decreasing frequency)•gamma rays (used to sterilise surgical instruments)•X-rays (used to find broken bones and in luggage security)•ultraviolet (used to treat skin problems and sterilise medical instruments)•visible light (used in medicine for eye surgery, to remove birthmarks and cancerous tumours)•infrared (used to speed up the recovery of injured muscles and tissues)•microwaves (mobile phones use this type of radiation to carry signals)•TV and radio waves

Each of the radiations travel at 300,000,000 m/s in a vacuum (or air).They are all transverse waves.The energy of radiation is directly proportional to its frequency.

Period:period = 1/frequency; period is in seconds.

Energy:All waves transfer energy.The higher the amplitude of a wave the greater the energy transferred by that wave.

Diffraction:Waves that can bend around obstacles in its path.Waves with longer wavelengths (lower frequencies) will diffract more than waves with shorter wavelengths (higher frequencies).From that rule, radio waves diffract more than TV waves.

Wave equation calculation

Wave equation calculation

Speed, distance and

time calculation

Speed, distance and

time calculation

MenuMenuPeriod

calculation

Period calculation

Click: Satellites

Click: Reflectors

Click: Light

Wave equation calculations

1. A radio wave has a wavelength of 200 m. Calculate its frequency.

frequency = speed / wavelength

= 300,000,000 / 200

= 1,500,000 Hz

2. A radio wave has a frequency of 900 kHz. Calculate its wavelength.

wavelength = speed / frequency

= 300,000,000 / 900,000

= 333 m

3. Red light has wavelength of 600 nm. Calculate (a) its frequency, (b) its period, (c) the time taken for red light to travel 36000 km.

(a) frequency = speed / wavelength

= 300,000,000 / 0.0000006

= 500,000,000,000,000 Hz

(b) period = 1 / frequency

= 1 / 500,000,000,000,000

= 0.000000000000002 s

(c) time = distance / speed

= 36,000,000 / 300,000,000

= 0.12 s.

Back to wavesBack to waves


Speed, distance and time calculations

1. Calculate how far a gamma ray has travelled in 0.0005 seconds. Express your answer in kilometres.

distance = speed x time

= 300,000,000 x 0.0005

= 150000 m

Since 1 km = 1000 m, then 150000 / 1000 = 150 km

2. The Sun is 150,000,000 km away from the Earth. (a) Calculate how long it takes light to travel from the Sun to the Earth.

time = distance / speed

= 150,000,000,000 / 300,000,000

= 500 s

(b) During a solar flare, the light ray and infrared radiation leave the Sun's photosphere at the same time and travel through a vacuum towards the Earth. Will the infrared ray reach the Earth before, after or at the same time as the light ray?

Explain your answer.

At the same time, because light and infrared travel at the same speed in a vacuum.


Period and frequency calculations

A water wave travels at a speed of 0.8 m/s. The distance between points A and B of the water waves is 0.6 m.

Calculate the water wave's (a) wavelength

(b) frequency

(c) period.

(a) 3 wavelengths = 0.6 metres

1 wavelength = 0.2 m

(b) frequency = speed / wavelength

= 0.8 / 0.2

= 4 Hz

(c) period = 1 / frequency

= 1 / 4

= 0.25 s

Curved dishes: receiversSignals travel long distance and lose energy. This means curved reflectors are used to strengthen the received signal from satellites or other sources. The reflector is curved so that weak signals are collected over a large area and brings to a point called the focus.The detector is placed at the focus so that it receives a strong signal. Radio and microwave telescopes are examples of telescopes that require a large curved reflector.

Curved dishes: transmittersCurved reflectors are also used to transmit a strong parallel beam of signal (light or other radiations in the electromagnetic spectrum). In a dish-transmitter, the source is placed at the focus and the curved reflector produces a parallel beam of signal.

Signals from a distant source.(Note: if signals travel long distance, then the incoming rays are parallel.)

detector placed at focus

detector placed at focus

A parallel beam of signal (any radiation from the electromagnetic spectrum.) This explains why car headlights emit a parallel beam of light.


Satellites - telecommunication and

space exploration

Satellites are used for telephone communications, TV programmes, weather information, checking on crops, information on the security of other countries and monitoring Earth's climate

The time taken for a satellite to complete one orbit of the Earth

depends on its height above the Earth: the higher the orbit of the

satellite, the longer its orbital period.

A geostationary satellite takes 24 hours to orbit the Earth. Such a satellite would stay above the

same point on the Earth's surface.

On Earth, a ground station would use a curved reflector transmitter to send a parallel beam signal.At the satellite, the signal is received by a curved dish, which is the amplified and re-transmitted (at a different frequency) back to a different ground station.


Space is usually considered to start at an altitude of 100 km.We need satellites because we cannot just send signals (radio or microwave) from the UK to Australia. This is because:* the signals from transmitters travel in straight lines (which happens with HF TV signals)* the Earth is curved and these signals cannot travel directly from Britain to Australia

There are hundreds of satellites orbiting the Earth. For example, a Sat Nav receiver compares the time it takes to receive radio signals from a number of satellites.

Spacecrafts:When a spacecraft re-enters the atmosphere, the craft's kinetic energy is converted into heat. This is due to the spacecraft experiencing friction friction with the atmosphere. A spacecraft must be covered with heat shielding to prevent it from burning up on re-entry.A blunt shaped spacecraft deflects the heat away from the spacecraft.

Click: ProjectilesSatellite motion:

Satellite motion is an extension of projectile motion.A satellite continually accelerates towards the Earth, just like any other projectile.However, the satellite is moving so fast that the Earth curves away from it as quickly as it falls.This means the satellite never reaches the Earth as it orbits the planet.

Light


Reflection of light:When light is reflected from a flat mirror, the angle of incidence, i, is equal to the angle of reflection, r.

Principle of reversibility:A ray of light will follow the same path in the opposite direction when it is reversed.

Optical fibres:An optical fibre is a thin thread of glass through which light can travel. Heat, however, is not transmitted along the fibre. The optical fibre is said to transmit 'cold light'.Light signals travel along the optical fibre at a speed of 200,000,000 m/s.Such glass fibres can carry telephone and modern telephone systems use both optical fibres and electrical cables.

Advantages of optical fibres:Advantages:* cheaper to make* lighter* greater signal capacity* better signal quality* less energy loss per km of optical fibre (i.e. fewer repeater stations)* smaller in size * not affected by interference.

In electrical wires, electrical signals travel at almost 300,000,000 m/s. Optical fibres are also difficult to join together.

How does an optical fibre work?Optical fibres work due to total internal reflection. This means light reflected inside the glass fibre and none escapes into the air. Total internal reflection occurs when the angle of incidence is greater than the glass' critical angle (which is around 42 degrees). From this set-up, light can travel through optical fibres without ever leaving the fibre.

light is reflected along the fibre

Endoscopes:Light is transmitted along the optical fibre. They are used to look inside a patient without the need for surgery.An endoscope has two bundles of fibres: one to transmit 'cold light' from the source down into the patient; the other bundle is used to send an image back to the surgeon's eye.Endoscopes are flexible and can move around inside the patient.

Refraction:Refraction is when light changes its velocity (speed and direction) as it passes from one medium into another.Remember: When light passes from air into glass, the refracted ray 'bends' (should be refract) towards the normal. When light passes from glass into air, it refracts away from the normal.

i

rnormal

air glass

i r

mirror

normal

Critical angle and total internal reflection:* When a light ray enters glass, along the normal, it does not change direction.* When light passes from glass into air, and the angle of refraction is 90 degrees, the angle of incidence is called the critical angle .* At angles greater than the critical angle, all the light is reflected back into the glass. This is called total internal reflection.

NUCLEAR RADIATION

Part 1

Menu

The atom:Most of the mass of an atom is found in a central nucleus. The atom is made up:* a nucleus contain positively charged protons (red) and neutral charged neutrons (blue)* negatively charged electrons orbiting the nucleus (green)

Types of radiation:* Alpha particles - slow moving helium nucleus. It can travel a few cm in air. They can be absorbed by thin paper.* Beta particles - fast moving electrons from the nucleus. They can travel a few metres of air. It can be blocked by a few mm of aluminium* Gamma rays - high energy and high frequency electromagnetic radiation. It is absorbed by a minimum of a few cm of lead.

Radioactive decay is a random process. Ionisation:This occurs when an atom loses or gains electrons to become an ion.Alpha particles produce much higher ionisation density than beta particles or gamma rays.This is because alpha particles are the largest and carry the greatest charge of all types of radiation.Alpha particles can ionise the greatest number of atoms near the surface of a body.

Activity:The activity is the number of decays per second. Activity is measured in becquerels (Bq).

activity = number of decays / time

* activity, A, is in becquerels (Bq)* number of decays, N* time, t, is in seconds (s).

Absorbed dose:The absorbed dose is the energy absorbed per kilogram mass (of the absorbing material).

absorbed dose = energy / mass

* absorbed dose, D, is in grays (G) or joules per kilogram (J/kg)* energy, E, is in joules (J)* mass, m, is in kilograms (kg).

Equivalent dose: This is a measure of biological harm. The equivalent dose is measured in sieverts (Sv). Typical annual equivalent dose is about 2 mSv.

equivalent dose = absorbed dose x radiation weighting factor

* equivalent dose, H, is in sieverts (Sv)* absorbed dose, D, is in grays (G)* radiation weighting factor, wR, is used to compare the ability of different types of radiation to damage living cells.

Half life:The half-life of a radioactive source is the time taken for its activity to fall to half of its original value.All radioactive sources have their own half-life.

To measure half-life you would:* measure background count rate first* then measure the count rate with the radioactive source present over an appropriate period of time using a Geiger-Muller tube and counter.* background activity is subtracted from each reading and a graph of count rate against time is drawn.* the time taken for the activity to half can be determined from the graph.

Click: Half-life calculations

Click: Activity calculations

Click: Dosimetry calculations

Part 2

NUCLEAR RADIATION

Part 2

Medical uses of radiation:Radiation can kill or damage (change the nature of) living cells.Nuclear radiation can be used in medicine to:* sterilise medical instruments* kill cancerous cells (placing alpha particles next to the tumour / firing gamma rays at the tumour* diagnose medical problems (a radioactive tracer is injected and absorbed by an organ, which is then monitored by a gamma camera)

Non-medical use of radiation:* Beta particles are used to monitor paper thickness* monitor leaks in underground water and sewage pipes (by adding radioactive tracers to the liquids in the pipes and monitor traces of radioactivity in the soil surrounding them.* monitoring fertilisers and how it is being used in plants.

Effects of radiation on non-living things:Radiation can cause:* ionisation* fog photographic film* scintillations.

Ionisation is used to detect radiation in the Geiger-Muller tube.When radiation enters the low pressure gas tube, it ionises the gas and pulses of current passes between the electrodes. This pulse of current is recorded on a counter (which is connected to the tube).

In a film badge, different sections of the photographic film are covered by various thicknesses and types of absorbers. The type of radiation is determined by which sections of the film are blackened. The amount of radiation is determined by how black the film is.

In scintillation, certain materials absorb the energy of the radiation and re-emits it as light. These are used to detect radiation in a gamma camera.

Background radiation sources:Examples are:* cosmic radiation* the Earth (soil and rocks - granite)* the air (radon gas in air, from rocks and buildings)* the human body (K-40)* medical sources for X-ray and cancer treatment* nuclear reactors

Safety with radiation:* handle radioactive substances with forceps* never point radioactive sources at anyone* wash hands thoroughly after using radioactive sources* never bring radioactive sources up to your face (especially your eyes and mouth)* no one under 16 years of age should handle a radioactive source* always store radioactive substances in suitable lead-lined containers* keep a record of the use of all radioactive sources* return the source to its storage container after it has been used.

Reducing the equivalent dose:This can be reduced by:* shielding* limiting exposure time* increasing the distance from the source.

Menu

Nuclear reactions:Fission and fusion reactions release large amounts of energy.

Click: Nuclear fission

Click: Nuclear fusion

Part 1

Half-life calculations

1. A radioactive source has a half-life of 30 days. Calculate its activity 120 days after it was measured at 2000 kBq.

120 /30 = 4 half-lives

2000 to 1000 to 500 to 250 to 125

125 kBq

2. A source has an activity of 60 kBq and a half-life of 20 s. How long will it take for its activity to drop to 7.5 kBq?

Number of half-lives: 60 to 30 to 15 to 7.5 So that is 3 half-lives.

1 half-life is 20 s,3 half-lives is 20 x 3 = 60 s

3. A hospital technician is working with a radioactive source. The graph, on the right, shows the activity of the source over a period of time.

(a) Use information from the graph to calculate the half-life of the radioactive source.

when t = 0 hours, activity = 160 kBq

find t, when activity drops to 80 kBq

t = 6 hours

(b) Calculate the activity after five half-lives.

160 to 80 to 40 to 20 to 10 to 5

activity after 5 half-lives = 5 kBq

Part 1

Activity calculations

1. Calculate the number of decays in the sample in two minutes, when the activity of a source is 1.2 kBq.

number of decays = activity x time

= 1200 x (2 x 60)

= 144000 decays

2. Explain what is meant by an activity of 10 MBq.

10 million decays every second

Part 1

Dosimetry calculations

1. A 5 kg block absorbs 10mJ of slow neutrons. Calculate the absorbed dose received by the box.


= 0.01 / 5

= 0.002 Gy or 2mGy

2. A box receives an absorbed dose of 40 mGy from a radioactive source which emits alpha particles only. Calculate the equivalent dose received by the box.

equivalent dose = absorbed dose x radiation weighting factor

= 0.04 x 20

= 0.8 Sv

3. A 2 kg box absorbs 40 mJ of radiation. The equivalent dose received by the box is 200 mGy. Using the information, from the table, which radiation was absorbed by the box?

E = 0.04 J m = 2 kg H = 0.2 Gy Wr = ?

* Find absorbed dose, D, first.


= 0.04 / 2

= 0.02 Gy

* Now find Wr.

radiation weighting factor = equivalent dose / absorbed dose

= 0.20 / 0.02

= 10

From the table, the radiation is fast neutrons.

Type of radiationType of radiation radiation weighting factorradiation weighting factor

alphaalpha 2020

betabeta 11

gammagamma 11

fast neutronsfast neutrons 1010

slow neutronsslow neutrons 33Part

1

Nuclear fission

1. A bombarding neutron is absorbed by the large nucleus.2. The large nucleus becomes unstable and breaks apart producing fission fragments.3. Neutrons are released in this nuclear reaction, which then bombards other large nuclei. This avalanche of nuclear fission is known as a chain reaction.

Back to nuclear

radiations

Back to nuclear

radiations

Nuclear fusion:

1. Two lighter nuclei (two hydrogen nuclei, each consists of two neutrons and one proton) combine (fuse) together2. The two nuclei fuse to form a heavier nucleus (helium) and energy is released3. The products (heavy nucleus and the two neutrons) have kinetic energy and move away.

DYNAMICS: Part 1

Forces:One newton is a force required to accelerate a kilogram mass at 1 m/s/s.

A force can change an object's speed, shape and direction.

Friction is a force that acts in a direction opposite to motion.

Balanced force: two forces, both equal in size and act in opposite directions are called balanced forces.

Speed, distance and time:Speed is the distance, travelled by an object, in one second.

Average speed (v-bar), of an object, is the total distance travelled divided by the time taken.

The instantaneous speed, of an object, is its speed at a particular point during its journey.

Acceleration:The acceleration, of a vehicle, is the change in speed over the time taken for the change.

acceleration = change in speed / time

OR a = (v - u) / t

a - acceleration (m/s/s)v - final velocity (m/s)u - initial velocity (m/s)t - time taken (s)

If a = 0 m/s/s, the object is stationary or travelling at a constant velocity.If a > 0 m/s/s, the object is speeding upIf a < 0 m/s/s/, the object is slowing down.

Speed-time graph:

Newton's third law of motion:If an object A exerts a force on B, then B exerts and equal and opposite force on A.

Newton's first law of motion:A body will remain at rest or move at a constant speed in a straight line unless acted on by an unbalanced force.

Newton's second law of motion:When an object is acted on by a constant unbalanced force, the body moves with constant acceleration in the direction of the unbalanced force.

Basically,

F = m x a

F - unbalanced force (N)m - mass (kg)a - acceleration (m/s/s).

Part 2 Menu

Interplanetary flight:During interplanetary flight, there is no need for the engines to be kept on.Since space is a vacuum, there is no friction acting on the vehicle. With no unbalanced forces acting on it, the vehicle will continue to move at a steady speed. (Newton's 1st Law of motion).

Click: speed-time graph

Click: example

Click: example

Click: example

Click: example

DYNAMICS: Part 2

Work done:Work done is a measure of how much energy is transferred.

work done = force x distance Ew = F x d

work done, Ew, is in joules (J)force, F, is in newtons (N)time, t, is in seconds (s).

Projectiles:

When an object is projected in a gravitational field, it will follow a curved path. This is known as projectile motion.

In projectile motion, there are two types of motion: * vertical - object is accelerating downwards due to the object's weight* horizontal - object is travelling at a constant speed (provided air resistance is negligible)

Velocity and displacement:Displacement - a measure of how far two points are away from each other, in a given direction.Velocity - rate of change of displacement:

velocity = displacement / timeAcceleration - rate of change of velocity: acceleration = change in velocity / time

Scalars and vectors:* Scalar quantity has a size (magnitude) only e.g. temperature, mass, speed, distance, time, energy, distance and power.* Vector quantity has a size and direction e.g. velocity, acceleration, force, weight, pressure and displacement.

Velocity-time graph:

Part 1

Click: Projectiles

Weight:The weight of an object is the force on it due to the planet's gravitational pull.Weight is measured in newtons.

The mass of an object is the amount of matter that makes up that object.It is measured in kilograms.

Weight = mass x gravitational field strength

W = m x g

W -weight in newtons (N)m - mass in kilograms (kg)g - gravitational field strength in newtons per kilogram (N/kg)

The gravitational field strength, g, of a planet is the weight per unit mass of an object on that planet.

Click: example

Click: example

Free fall:When an object is in free fall, it appears to be weightless. Astronauts, inside a spacecraft, appear to be weightless because both the astronauts and the craft are falling towards the Earth at the same rate.

Click: velocity-time graph

Click: example

Click: example

Menu

speed (m/s)

speed (m/s)

speed (m/s)

time (s)

time (s)

time (s)

accelerating

decelerating

constant speed

speed (m/s)

time (s)

12

34

The speed-time graph, shown above, consists of four stages. We can work out how far an object has travelled by working out the area under the graph.The total distance is given as:

distance = area under graph = area 1 + area 2 + area 3 + area 4

The acceleration and deceleration can be worked out by using the formula:

acceleration = (final speed - initial speed) / time taken

From the above graph: during stage 1 - the object is accelerating;stage 2 - acceleration = 0 m/s/s/;stage 3 - object is accelerating, and stage 4 - object is decelerating.

Part 1

velocity (m/s)

velocity (m/s)

velocity (m/s)

time (s)

time (s)

time (s)

accelerating

decelerating

constant speed

velocity (m/s)

time (s)

12

34

The velocity-time graph, shown above, consists of four stages. We can work out how far an object has travelled by working out the area under the graph.The total displacement is given as:

displacement = area under graph = area 1 + area 2 + area 3 + area 4

The acceleration and deceleration can be worked out by using the formula:

acceleration = (final speed - initial speed) / time taken

From the above graph: during stage 1 - the object is accelerating;stage 2 - acceleration = 0 m/s/s/;stage 3 - object is accelerating, and stage 4 - object is decelerating.

Part 2

velocity (m/s)

time (s)

12

3

4 5

010 30 40 50 60

20

-20

A velocity-time graph for the motion of a vehicle is shown.

•Describe the motions represented by each part of the velocity-time graph.

(b) Calculate the acceleration during each part of the graph.

(c) Calculate the displacement during each part of the journey.

(d) Calculate the length of the journey.

Solution:

• 0 to 10 s: constant acceleration from 0 to 20 m/s, in 10s. 10 to 30 s: uniform (constant) velocity of 20 m/s for 20 s.

30 to 40 s: constant deceleration from 20 m/s to 0 m/s

at 40 s: vehicle changes direction

40 to 50 s: vehicle accelerates in opposite direction, from 0 to 20 m/s, in 10 s.

50 to 60 s: vehicle decelerates (in the same direction as 40 to 50s), from 20 m/s to 0 m/s.

(b) 0 to 10 s: u = 0 m/s, v = 20 m/s, t = 10 s

a = (v-u) / t

= (20 - 0) / 10

= 2 m/s/s

30 to 40 s: u = 20 m/s, v = 0 m/s, t = 10 s

a = (v-u) / t

= (0 - 20) / 10

= -2 m/s/s

40 to 50 s: u = 0 m/s, v = -20 m/s, t = 10 s

a = (v-u) / t

= (-20 - 0) / 10

= -2 m/s/s

50 to 60s: u = -20 m/s, v = 0 m/s, t = 10 s

a = (v-u) / t

= (0 - -20) / 10

= 2 m/s/s

10 to 30 s: acceleration = 0 m/s/s

Part 2

(c) + (d)

(c) displacement = area between graph and time axis

from 0 to 10s: displacement = (0.5 x 10 x 20) = 100 m

from 10 to 30s: displacement =(20 x 20) = 400 m

from 30 to 40s: displacement = (0.5 x 10 x 20) = 100 m

from 40 to 50s: displacement =(0.5 x 10 x -20) = -100 m

from 50 to 60s: displacement = (0.5 x 10 x -20) = -100 m

(d) length of journey = displacement

= 100 + 400 + 100 + (-100) + (-100)

= 400 m previous

A runner completes a 400 m race in 50 s.Calculate her average speed.

average speed = distance / time

= 400 ./ 50

= 8 m/s

A toy car, of length 5 cm, takes 0.025 s to pass through a light gate. Calculate the toy car's instantaneous speed.

instantaneous speed = length of car / time taken

= 0.05 / 0.025

= 2 m/s

Part 1

Average speed and instantaneous speed

Part 2

Weight

An astronaut has a mass of 80 kg. Calculate his weight on (a) Earth (g = 9.8 N/kg), (b) Saturn (g = 3.7 N/kg) and

(c) Mars (g = 3.7 N/kg).

Solutions:

• W = m x g

= 80 x 9.8

= 784 N

(b) W = m x g

= 80 x 9.0

= 720 N

(c) W = m x g

= 80 x 3.7

= 296 N

Part 2

Work done

1. A man does 40000 J of work in moving a wheel barrow 50 m. What average force does he exert?

2. There is a frictional force of 1000 N acting on a car and the resultant force is 4000 N. If the car travels 3 km, what is the work done by the car's engine?

work done = force x distance

force = work done / distance

= 40000 / 50

= 80 N

engine force = 1000 + 4000 = 5000 N

work done = force x distance

= 5000 x 3000

= 15000000 J

Acceleration

1. A trolley takes 12 s to reach 6 m/s from rest. Calculate its acceleration.

a = (v - u) / t

= (6 - 0) / 12

= 0.5 m/s/s

2. A car decelerates at 1.5 m/s/s for 14 s from a initial speed of 27 m/s. Calculate its final speed.

v = ? u = 27 m/s a = -1.5 m/s/s t = 14s

v = u + at

= 27 + (-1.5 x 14)

= 6 m/s

3. The superhero, Beakman, accelerates at 5 m/s/s for 10 s to reach a final speed of 70 m/s. Calculate Beakman's initial speed.

a = 5 m/s/s, t = 10 s, v = 70 m/s, u = ?

v = u + at

70 = u + (5 x 10)

70 = u + 50

u = 70 - 50 = 20 m/s

4. A car travelling at 20 m/s decelerates at 4 m/s/s. Calculate the time taken for the car to reach a complete stop.

u = 20 m/s, a = -4 m/s/s, v = 0 m/s, t = ?

v = u + at

0 = 20 + (-4 x t)

4t = 20

t = 5 s

Part 1

Part 1

A rocket has a mass of 10000 kg and sits on a launch pad.

• Calculate the rocket's weight on the Earth's surface. Note: g = 9.8 N/kg.

(b) During lift-off, the rocket's engine thrust is 200 kN. Calculate the rocket's unbalanced force.

(c) Calculate the rocket's initial acceleration during lift-off.

(d) An identical rocket, with the same mass and engine thrust takes off from Mars. What effect does this have on the rocket's initial acceleration on Mars? Justify your answer.

Solution:

(a) W = m x g

= 10000 x 9.8

= 98000 N

(b) unbalanced force = 200000 - 98000

= 102000 N

(c) acceleration = unbalanced force / mass ( a = F / m)

= 102000 / 10000

= 10.2 m/s/s

(d) * rocket's weight is smaller, since g on Mars is less than that on Earth * rocket's unbalanced force increases

* acceleration is bigger

0 30

10

25

time (s)

speed (m/s)

A car's speed-time graph is shown.

•Describe the car's motion from 0 to 30 s.

(b) Calculate the car's acceleration.

(c) Calculate how far the car travelled during the first 30 seconds of its journey.

Solution:

• the car is accelerating from 10 m/s to 30 m/s, in 30 seconds

(b) a = (v - u) / t

= (25 - 10) / 30

= 0.5 m/s/s

(c) distance travelled = area between graph and time axis

= (10 x 30) + (0.5 x 30 x 15)

= 300 + 225

= 525 m

Part 1

Velocity and displacement calculation

A car starts from rest, at point S, and travels 240 m due North. It then travels 100 m due East and finishes at point F. It took the car 25 s to travel from point S to point F.

(a) Calculate the car's displacement at point F relative to point S.

(b) Calculate the car's average velocity between points S and F.

Solution:

(a) Draw a triangle to show the car's motion from start (S) to finish (F).

There are two ways to solve this problem: scale drawing

OR Pythagoras' theorem and trigonometry.

If you use scale drawing and use a scale, for example, 1 cm represents 20 m.

You should find that the length between S and F is 12.5 cm, which represents 250 m.

Since displacement has a direction, then the position F relative to S is 23 degrees.

(b) average velocity = displacement / time

= 250 / 25

= 10 m/s at a bearing of (023)

Part 2

E Click to show lines of vertical

displacement

Click to show lines of horizontal displacement

Projectiles and free fall.

Back to dynamics

The ball is accelerating downwards. The lines represent the position of the ball after each second.

On Earth, all objects free fall. This is because an object has a mass and its weight is pulling that object towards the ground. The acceleration due to gravity is 9.8 metres per second squared.

Vertical motion.

Click to show lines of horizontal displacement

Click to show simulation

In vertical motion, the initial vertical velocity is 0 m/s. Final vertical velocity is worked out from

v = u + at.

where a = 9.8 m/s/s, u = 0 m/s, t is the time (during its fall) in seconds. Back to dynamics

Horizontal motion.

Click to show simulation

Assuming that air resistance is negligible, the horizontal distance travelled each second is the same.The ball's horizontal speed is constant.

horizontal distance = horizontal speed x time

Back to dynamics

SPACE

Light year (ly): The distance, travelled by light (in a vacuum), in one year.(e.g. Earth is 4.3 ly from Proxima Centauri, 100,000 ly from the edge of our galaxy and 2.6 million ly from Andromeda (M31).

Light year (ly): The distance, travelled by light (in a vacuum), in one year.(e.g. Earth is 4.3 ly from Proxima Centauri, 100,000 ly from the edge of our galaxy and 2.6 million ly from Andromeda (M31).

The Universe:

Solar System: Our Sun, with all the planets, moons and other objects orbiting around it.A galaxy contains billions of stars. Our galaxy is called the Milky Way.A planet is a large ball of matter that orbits a star. Planets do not give off light themselves, but they do reflect light from its central star.An exoplanet is a planet orbiting around another star. For life to exist on an exoplanet, the planet should have an atmosphere, liquid water, and it is neither too hot or too cold.A moon is a natural satellite, which orbits a planet. A star is a hot dense object, undergoing nuclear fusion, and giving off light. It contains around 90% hydrogen, 9% helium and other elements.The Universe consists of many galaxies separated by empty space.

The Universe:

Solar System: Our Sun, with all the planets, moons and other objects orbiting around it.A galaxy contains billions of stars. Our galaxy is called the Milky Way.A planet is a large ball of matter that orbits a star. Planets do not give off light themselves, but they do reflect light from its central star.An exoplanet is a planet orbiting around another star. For life to exist on an exoplanet, the planet should have an atmosphere, liquid water, and it is neither too hot or too cold.A moon is a natural satellite, which orbits a planet. A star is a hot dense object, undergoing nuclear fusion, and giving off light. It contains around 90% hydrogen, 9% helium and other elements.The Universe consists of many galaxies separated by empty space.

Detectors of radiation:Celestial objects, such as the stars and galaxies, give out energy over the whole range of the electromagnetic spectrum. Different types of telescopes are required to detect different types of e-m radiation.

* Gamma rays - Geiger Muller tube* X-rays - photographic film* Ultraviolet - florescent paint* Visible light - photographic film* Infrared - blackened thermometer / thermogram* Microwaves - diode probe* TV and Radio - aerial.

Detectors of radiation:Celestial objects, such as the stars and galaxies, give out energy over the whole range of the electromagnetic spectrum. Different types of telescopes are required to detect different types of e-m radiation.

* Gamma rays - Geiger Muller tube* X-rays - photographic film* Ultraviolet - florescent paint* Visible light - photographic film* Infrared - blackened thermometer / thermogram* Microwaves - diode probe* TV and Radio - aerial.

Colour and wavelength:White light is made up of a range of colours, which can be separated by splitting the white light with a prism (to obtain a spectrum).Colours of the spectrum (in order of decreasing wavelength are: red, orange, yellow green, blue, indigo and violet.Red light has a wavelength of 700nm; violet light - 400 nm.

Colour and wavelength:White light is made up of a range of colours, which can be separated by splitting the white light with a prism (to obtain a spectrum).Colours of the spectrum (in order of decreasing wavelength are: red, orange, yellow green, blue, indigo and violet.Red light has a wavelength of 700nm; violet light - 400 nm.

Line spectrum:This consists of a continuous spectrum with certain colours missing which appear as black in the spectrum. Line spectra analysis allows the elements present in a star to be identified.Here is an example.

Line spectrum:This consists of a continuous spectrum with certain colours missing which appear as black in the spectrum. Line spectra analysis allows the elements present in a star to be identified.Here is an example.

The age of the universe:This can be estimated by measuring the average temperature of space. From this measurement, the age of the Universe is 13.8 billion years.

The age of the universe:This can be estimated by measuring the average temperature of space. From this measurement, the age of the Universe is 13.8 billion years.

MenuMenu

Cosmic radiation:The Earth is bombarded with sub-atomic particles called cosmic rays. Other types of particles bombard the Earth: electrons, protons, helium nuclei, antimatter and nuclei of heavy elements.

Cosmic radiation:The Earth is bombarded with sub-atomic particles called cosmic rays. Other types of particles bombard the Earth: electrons, protons, helium nuclei, antimatter and nuclei of heavy elements.

Light year calculation

Light year calculation

Click: Space Exploration

Calculations on the light year.

The distance from Earth to the nearest star, Proxima Centauri, is 4.3 light years

• Calculate the distance light would travel in one year.

distance = speed x time

= 300,000,000 x (365.25 x 24 x 60 x 60)

= 9.45 x 10^15 metres

(b) Calculate the distance between Earth and Proxima Centauri.

distance = 9.45 x 10^15 x 4.3

= 4.07 x 10^16 metres.

(c) Estimate the month and year in which light radiated on 15th May 2014, from Proxima Centauri, will be seen on Earth.

0.3 years = 0.3 x 12 = 4 months

So, 4.3 ly = 4 years and 4 months.

Month and year of observation - September 2018.

Back to spaceBack to space

ENERGY

Kinetic energy:This is known as moving energy.

Gravitational Potential energy:This is the work done in lifting a mass, m, at a height, h, above the ground.

Efficiency:The energy and power percentage efficiency is expressed as:

Conservation of energy (part 1):

Heat energy

Changes of state:There is no change temperature when a change of state occurs.

Latent heat of fusion:The energy required to change 1 kg from solid at its melting point to liquid without a change in temperature.

Latent heat of vaporisation:The energy required to change 1 kg of a liquid at its boiling point into 1 kg of vapour without a change in temperature.

Change in temperature:The specific heat capacity, of a substance, is the amount if energy (in joules) needed to change the temperature of 1 kg by 1 degree Celsius.

Conservation of energy (part 2):

Some of the heat energy supplied will be lost to the surroundings This means that the substance will take in less energy than was supplied by the heater.

In most heat problems we can assume no energy is lost to the surroundings.

Generating electricity:* Thermal power stations change chemical energy of the fuel into electrical energy.* A nuclear power station changes the nuclear energy of the uranium fuel into electrical energy.* A hydroelectric power station changes the gravitational potential energy of water behind a dam into electrical energy.* A nuclear power station produces radioactive waste.

Click: Kinetic energy calculations

Click: Potential energy calculations

Click: Conservation of energy

calculation

Click: efficiency calculations

Click: Conservation of energy

calculation

Click: heat energy

calculations

Click: latent heat energy

calculations

Power, energy and time:

power = energy / time

Menu

Kinetic energy

1. A 70 kg man on a 20 kg bicycle is moving at a steady speed of 6 m/s when he applies the brakes and comes to rest in 4 seconds.

Calculate the kinetic energy of the man and his bicycle before he brakes.

2. A toy car of mass 0.1 kg, rolls across the floor. Its kinetic energy is 0.45 J.

Calculate the toy car's speed..

Energy

Potential energy

Energy

1. A ball has a mass of 0.5 kg and is raised 12 m above the ground. Calculate the ball's gain in potential energy.

2. An object is raised 20 m above the ground and gains 980 J of gravitational potential energy. Calculate the mass of the object.

Conservation of energy

Energy

A 5 kg ball is raised 10 m above the ground. It is then released and hits the ground.

(a) Calculate the potential energy at the top of the cliff.

(b) State the kinetic energy at the bottom of the cliff, assuming that there is no air resistance.

(c) Calculate the speed of the ball at the bottom of the cliff.

(d) Which piece of information given in the question is not required to find the speed?

Efficiency

Energy

1. A power station uses up to 300 MJ of chemical energy to produce 180 MJ of electrical energy. Calculate the efficiency of the power station.

2. A power station is 35% efficient. If it produces 400 MJ of electrical energy per second, calculate the input power to the station.

Conservation of energy

An immersion heater takes 15 minutes to raise the temperature of 0.5 kg of water from 20C to 60C.

•Calculate the power rating of the heater.

(b) The heater is connected to a 12 V supply. Calculate the current in the element.

Energy

Latent heat

Energy

Calculate the energy required to change 2.6 kg of water at 100 degrees Celsius into steam at the same temperature.

Calculate the energy required to change 2.6 kg of ice at 0 degrees Celsius into water at the same temperature.

Changes in temperature

Energy

The mass of water is 0.2 kg and its starting temperature is 18 degrees Celsius.

Calculate the final temperature of water when it is suppled by 100000 J of heat energy.

ELECTRICITY: Part 1

Current:The electric current is the rate of flow of charge.It is measured in amperes (A).

charge = current x time Q = It

charge, Q, in coulombscurrent, I, in amperestime, t, in seconds.

Voltage:The voltage is the electrical energy given to each coulomb of charge. It is measured in volts (V).

Resistance:Resistance is a measure of opposition to current in a circuit. It is measured in ohms.

resistance = voltage / current R = V / I

resistance, R, in ohmsvoltage, V, in voltscurrent, I in amperes

The above expression is known as Ohm's Law.

Series circuit rules:

* The current is the same at all points in a circuit* The voltage across each component adds up to the supply voltage.

Resistors in series:

Resistors in parallel:

Parallel circuit rules:

* The current in each branch adds up to the supply current.* The voltage across each branch is equal to the supply voltage.

Power:This is the energy transferred every second. It is measured in watts (W).Potential divider:

A potential divider circuit consists of a number of resistors connected across a supply. The bigger the resistance, the bigger the potential difference across that resistor.

Part 2

Menu

ELECTRICITY: Part 2

Power:Earlier, power is defined as the rate at which energy is transferred.

This can be written as:

power = energy / time P = E / t

power, P, is in watts (W)energy, E, is in joules (J)time, t, is in seconds (s)

Mains frequency and voltage:In the UK, the quoted mains supply is 230 V and mains frequency is 50 Hz.

The peak value of an a.c. supply is greater than the declared value (root mean square value)

More about resistance:

* The larger the resistance in a circuit, the smaller the current in that circuit (provided the supply voltage is the same).* When a conductor heats up, the particles in that conductor vibrate more and its electrical resistance increases.* The resistance of a lamp increases as the current in the lamp increases. From that, you can only use Ohm's Law, for any conductor, at a constant temperature.* For a resistor, at constant temperature, V/I = constant.* Connecting resistors in series INCREASES the total resistance.* Connecting resistors in parallel DECREASES the total resistance.

Transmission lines:Transformers are used to reduce power loss in electrical transmission.This is done by operating the transmission lines at a high voltage.Step-up transformers are used to increase the voltage from the power station. The transmission lines then carry electricity round the country.. Step-down transformers are then used to reduce the voltage to suitable levels for industries and homes.

To calculate the power loss, you use the formula:

power loss = current x current x resistance P = I x I x R

a.c. and d.c.:

a.c. (alternating current) is when current passes round the circuit, back and forth, many times per second.The mains supplies a.c.

d.c. (direct current) is when current passes round the circuit in one direction only. Batteries and cells supply d.c.

The difference between d.c. and a.c. can be seen by connecting the supplies to an oscilloscope.

d.c. a.c.

Click: circuit problems

Part 1

Transistor:A transistor acts like a switch.There are two types of transistor:npn-transistor and n-channel enhancement MOSFET.

Click: example

Menu

A student draws up a circuit and assembles it. The ammeter displays a reading of 3 A.

•Is this a series or a parallel circuit?

(b) The potential difference (voltage) across the resistor, R, is 8 V. State the voltage across the lamp.

(c) The lamp is fully operated at this voltage. Calculate the lamp's power rating.

(d) Calculate the resistance of the lamp, which operating at this voltage.

(e) The lamp was left on for 15 minutes. Calculate the electrical energy that was transferred during that time.

----------------------------------------------------------------------------------------------------------------------

Solutions:

•series circuit

(b) 4 V (12 - 8 = 4V)

(c) P = V x I = 4 x 3 = 12 W

(d) R = V / I = 4 / 3 = 1.33 ohms

(e) E = P x t = 12 x (15 x 60) = 10800 W or 10.8 kW

Circuit problem 1

Part 2

Click: circuit problem 2



Part 2


Circuit problem 2

(a)Calculate the total resistance in this circuit.

(b) Calculate the current in the 20 ohm resistor.

(c) Calculate the potential difference (voltage) across the 10 ohm resistor.

Solutions:


Part 2


Circuit problem 3

(a) Calculate the total resistance of the parallel network of resistors.

(b) Calculate the circuit's total resistance.

(c) Calculate the current reading, which should be displayed on the ammeter.

(d) Calculate the potential difference across the 10 ohm resistor.

A circuit diagram of an alarm system is shown.

• From the circuit diagram, Identify an output device.

(b) State the circuit symbol circled yellow.

(c) The device, circled yellow, switches on when the voltage at the base is 0.7 V. A fixed resistor, R, has a resistance of 10 kilo- ohms. Calculate the resistance of the LDR when the potential difference across it is 0.7 V.

(d) Explain how this alarm system operates..

Solutions:

Part 2

Mindmap nat5ppt

Documents

Transcript of Mindmap nat5ppt