Q#1 Fig. 4.1 shows a hydroelectric power station.

Water from the lake is used

to produce electricity in the turbine house.

(a) State where the water in Fig. 4.1 has the least potential energy.
.................................................................................................................................... [1]

(b) In 30 minutes, the water loses 5.0 × 109 J of energy and 4.5 × 109 J of
electrical energy is produced in the turbine house.
(i) Calculate the efficiency of the energy conversion.

efficiency = ........................... [1]

(ii) Calculate, in watts, the electrical power output from the turbine house.

power = ............................W [3]

(c) Some power stations burn coal to produce the same electrical power
output. State one advantage of the hydroelectric power station.
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [1]
(d) State one harmful effect that the hydroelectric power station may have
on the environment.

..........................................................................................................................................
.................................................................................................................................... [1]
Q#2 The mobile phone contains a rechargeable battery.Energy is stored inside the battery as it
is charged.Describe the useful energy change that takes place inside the battery as it is charged
from the mains.
....................................................................................................................................
....................................................................................................................................
...............................................................................................................................[2]
Q#3 The electrical power input to the kettle is 2000 W and the kettle is
used for 6 minutes (0.1 hour).Calculate the electrical energy, in J,
supplied to the kettle. State clearly the formula that relates power,
energy and time.
Q#4 When a car driver sees an emergency ahead, he applies the brakes.
During his reaction time the car travels at a steady speed and covers a
distance known as the thinking distance. The braking distance is the
distance travelled by the car after the brakes are applied.
State the energy change that occurs as the car brakes.
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]
Q#6 Fig. 6.1 shows a device used to generate electricity. Water entering
at the top turns the wheel. A generator connected to the wheel

produces electric current.

(a) State the two main energy changes that take place in this device as
water starts to flow.
1.....................................................................................................................................
2................................................................................................................................[2]
(b) The change in the potential energy of the water every second is 2000 J. The electrical
energy output is 1200 J every second. Calculate the efficiency of the process.
efficiency = ....................................... [2]

(c) State two ways in which the device wastes energy.

1. ......................................................................................................................................
2. ................................................................................................................................ [2]
Q#7 Fig. 1.1 is a block diagram of a power station.
The four boxes represent different parts of the power station. The first
box is labelled boiler.

Each of the other three boxes should contain one of the labels from the
following list.
generator, motor, transformer, turbine, solar panel
(a) On Fig. 1.1, label the boxes using words from the list. [2]
(b) State one environmental problem caused by burning oil to produce electricity.
 ..........................................................................................................................................
.....................................................................................................................................[1]
(c) Oil is a non-renewable energy source.
(i) State why oil is described as a non-renewable energy source.
..................................................................................................................................
..................................................................................................................................
................................................................................................................................... [1]
(ii) State one renewable energy source.
..................................................................................................................................
.................................................................................................................................... [1]

#9Fig. 10.1 shows the horizontal forces as a cyclist travels forwards.

The total mass of the bicycle and the cyclist is 75 kg. At one instant, the
speed of the bicycle is 4.0 m / s, the driving force is 30 N and the air
resistance is 20 N.
Calculate
(i) the total kinetic energy of the bicycle and the cyclist,

[3]
(ii) As the bicycle moves, energy is transmitted from the pedals to the ack
wheel. Fig. 10.2 shows what happens to the energy input to the pedals.

As energy is transmitted to the back wheel, some is lost.

Explain how this happens.
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]
(iiI) Calculate the efficiency of the bicycle in transmitting energy from the pedals to the back wheel.
Q#10 Fig. 2.1 shows a boat stationary in still water in a narrow tunnel.To move the boat, two men lie on
the top of it and push against the tunnel roof with their legs. They exert a total forward force of 1680 N on
the boat.
(a) The men push the boat 50.0 m to the end of the tunnel. Calculate the work
done on the boat by the men.

work done = ............................................ [2]

(b) Explain why the kinetic energy of the boat at the end of the tunnel is
less than the work done on the boat by the men.
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]

Q#11 A space research organization plans to send astronauts to Mars to examine rocks on its
surface. The organization will produce a report containing information about conditions on
Mars.
(i) A rock dropped on Mars falls to the surface. State the acceleration of the falling rock.
Assume that there is no air resistance on Mars.

[1]
(ii) Calculate the kinetic energy of a 0.50 kg rock as it strikes the surface at a
speed of 3.2 m/s.

[3]
Q#12 A rock climber climbs up a rock face, as shown in Fig. 12.1.

(a) To climb the rock face, the climber must do work.

Which force must the climber work against as he climbs? Tick one box.
 (b) What other quantity, as well as the force ticked in (a), must be known in
order to find the
work done by the climber?
.....................................................................................................................................[1]
(c) One climber weighs 1000 N and another weighs 800 N. They both take
the same time to climb the cliff.
(i) Which one has done the most work?
........................................................................
(ii) Which one has the greater power rating?
.................................................................[2]

(d) When the first climber reaches the top, he has more gravitational
potential energy than he had at the bottom.
(i) What form of energy, stored in his body, was used to give him this extra
gravitational potential energy?
..................................................................................
(ii) Where did he get this energy from?

..........................................................................[2]

Other than increasing gravitational potential energy on the way up, how else was energy in his
body used? State one way.
...................................................................................................................................
...................................................................................................................................[3]
Q#13 In Fig. 4.1, a small bird, a large bird and a squirrel are on the ground under a tree.

A loud noise scares the two birds. They both fly up to the top of the
tree.
(a) (i) Which bird does the most work raising itself to the top of the tree?
................... [1]
(ii) Explain your answer to (a)(i).
.................................................................................................................................... [1]
(b) A squirrel has the same weight as the large bird. It climbs the tree, to
the same height as the birds.
How does the increase in the squirrel’s gravitational potential energy
compare with that of each of the two birds? Answer the question by
completing the sentences below. Compared with that of the small bird, the
 increase of the squirrel’s potential energy is _______________
Compared with that of the large bird, the increase of the squirrel’s
potential energy is________________ [2]
(c) Which creature has the least gravitational potential energy when they
are at the top of the tree?
....................................................................................................................................[1]
(d) The small bird flies back down to the ground. What happens to the gravitational
potential energy it had at the top of the tree?
.....................................................................................................................................[2]

Q#14 (a) An electrician climbs up to the

platform of a special tower, in order to reach a
high-level spotlight, as shown in Fig. 4.1. Which
form of energy, possessed by the electrician’s
body,
1:is greater at the top of the tower than
it was at the bottom _________
2:is less at the top of the tower than it
was bottom? _________

(b) One of the electrician’s assistants also climbs up to the

platform. The assistant weighs less than the electrician.
Which of the two people does the most work climbing up to the platform,
and why?
Which person? .........................................
Why?.......................................................................................................................
............................................................................................................................. [3]
(c) The electrician wishes to know what power he develops as he climbs
the tower. Which quantities does he need to know in order to do this?
..........................................................................................................................................
.....................................................................................................................................[1]
Q#15 (a) Fig. 3.1 represents the energy into and out of a machine.

Write down the equation linking I, U and W.

..........................................................................................................................................
.................................................................................................................................... [1]
 (b) An electric motor and a pulley in a warehouse are being used to lift a
packing case of goods from the ground up to a higher level. This is shown in
Fig. 3.2.

The packing case of goods, the chains and the pallet together weigh 850 N.
(i) State the value of the tension force in the cable when the load is being
lifted at a steady speed.
tension force = ........................................ N [1]
(ii) When the load is just leaving the floor, why is the force larger than your
answer to (b)(i)?
..........................................................................................................................................
.................................................................................................................................... [1]
(iii) The warehouse manager wishes to calculate the useful work done
when the load is lifted from the ground to the higher level. Which quantity,
other than the weight, does he need to measure?
..........................................................................................................................................
.................................................................................................................................... [1]

(iv) Which further quantity does the manager need to know, in order to calculate the power
required to lift the load?.................................................................................................................................... [1]
(c) How does the electrical energy supplied to the electric motor compare
with the increase in energy of the load? Answer by completing the
sentence below.
The electrical energy supplied to the motor is ………………………………the increase in energy of
the load. [1]
Q#16 (a) Here is a list of some energy resources which might be used to
generate electricity. Put a tick in the box alongside any of these which
relies on a fuel being consumed.

(b) Here is a list of devices which convert energy from one form to another. battery, electric motor, gas
lamp, gas fire, generator, loudspeaker, microphone Which of these is designed to convert.
chemical energy into light energy,
..................................................................................................................................
electrical energy into mechanical energy,
..................................................................................................................................
sound energy into electrical energy?
...............................................................................................................................[3]
 Q#17 4 Two geologists are collecting rocks
from the bottom of a cliff. The rocks are
loaded into a
basket and then pulled up the cliff on the end
of a rope, as shown in Fig. 4.1. The basket of
rocks is brought to rest at the top of the cliff.
(i) Which form of energy that the basket possesses is
significantly greater at the top of the cliff than when it is at the
bottom of the cliff?
............................................................................................................................ [1]
(ii) Which two measurements must be made in order to calculate the increase in energy in (i)?
1. ..............................................................................
2. ............................................................................. [2]
(a) Which form of energy in his body has the man at the top of the cliff
used in order to raise the basket of rocks?
.............................................................................................................................. [1]
(b) State the measurement needed, in addition to those in (a)(ii), in order to
calculate the useful power developed by the man at the top of the cliff.
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]

Q#18 Fig. 3.1 shows a rock-fall down a mountain-side.

The rocks higher up the mountain were disturbed by something and they
roll down the mountain until they stop at the bottom. In the boxes below,
write the name of the type of energy being described.

[5]
Q#19 A child is sitting on an oscillating swing, as shown in Fig. 4.1. At the top of the oscillation,
the child and swing are momentarily at rest.

(i) Use the names of appropriate types of energy to complete the

following word equation. Write on the lines in the boxes.

(ii) The child continues to sit still on the swing. The amplitude of the
oscillations slowly decreases.Explain why this happens.
(iii).............................................................................................................................
..................................................................................................................................[3]
Q#20 As a pole vaulter runs towards the jump, his pole is straight. When
he is jumping, the pole is bent, as illustrated in Fig. 2.1.

Unit Student’s
08 notes

(a) Which form of energy of the athlete increases as he accelerates towards

the jump?
..........................................................................................................................................
.................................................................................................................................... [1]
(b) Which form of energy is stored in the pole because it is bent?
..........................................................................................................................................
.................................................................................................................................... [1]
(c) Which form of energy of the athlete increases because he is rising
towards the bar?
..........................................................................................................................................
.................................................................................................................................... [1]
(d) Which two quantities need to be known in order to calculate how much
work is done lifting the athlete up from the ground to the bar?
.............................................................and .................................................................... [1]