The City School

Attock Campus

1 Fig. 1.1 illustrates the journey of a cyclist from point A to point B. Points A and B are at the
same height.

The cyclist starts from rest at A and pedals up and over a hill. Near the bottom of the hill, she
starts to brake and comes to rest at B.
(a) Describe the energy changes that take place as she pedals up the hill at constant speed..[3]
(b) Explain how the law of conservation of energy applies to the complete journey from A to B.1]
(c) At one point in the journey, the gravitational potential energy of the cyclist has increased by
5400 J. The mass of the cyclist is 60 kg. The gravitational field strength is 10 N / kg. Calculate
the height above A of the cyclist at this point. [2]

2 A man of mass 75 kg falls from a platform high above a lake.

Fig. 2.1a shows the man tied to the platform by a long elastic rope (bungee).
Fig. 2.1b shows the man when he has fallen 20 m. After this point the rope
begins to stretch.
Fig. 2.1c shows the man at 25 m below the platform where he is first stopped
by the rope.

(a) As the man falls, his gravitational potential energy changes.

(i) The gravitational field strength is 10 N / kg. Calculate the change in his
gravitational
potential energy as he falls through 20 m.
[2]
(ii) When he is 20 m below the platform, his kinetic energy is equal to the
change in his
gravitational potential energy calculated in (i). Calculate his speed at this
point. [3]
(b) State the energy changes that take place as he falls from 20 m to 25 m
below the
platform. Ignore the effect of air resistance.
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3 Fig. 3.1 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. 3.1, label the boxes using words from the list. [2]
(b) State one environmental problem caused by burning oil to produce electricity.

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(c) Oil is a non-renewable energy source.
(i) State why oil is described as a non-renewable energy source.

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(ii) State one renewable energy source.

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4 The graph shows how the height above the ground of a bouncing ball changes with time.

Which statement explains why the height of each peak decreases with time?
A Kinetic energy is converted to potential energy at each bounce.
B Kinetic energy is converted to thermal energy at each bounce.
C The ball gains energy on impact with the floor.
D The ball is wearing out.

5 Where is energy released by the fusion of hydrogen atoms to form helium?

A in a nuclear power station
B in a radioactive isotope
C in the core of the Earth
D in the core of the Sun
6 A crane lifts a weight of 1000 N through a vertical height of 30 m.
It uses 60 000 J of energy.
What is the efficiency of the crane?
A 20 % B 30 % C 40 % D 50 %

7 Which energy changes take place when a pedalling cyclist uses a generator (dynamo) to light
his bicycle lamp?
A chemical kinetic electrical light
B electrical chemical kinetic light
C kinetic chemical light electrical
D light electrical kinetic chemical

8 A ball is held at rest on one side of a curved track.

The ball is released. It rolls down one side of the track and part of the way up the other side. It then stops,
before rolling back down again. The height of the stopping point is less than that of the starting point.
What is the sequence of energy changes between starting and stopping for the first time?
A potential energy → kinetic energy → potential energy + heat
B potential energy → kinetic energy → heat → potential energy
C potential energy → heat → kinetic energy → potential energy
D potential energy → kinetic energy + heat → potential energy + heat

9 A mass hangs on a string fixed at point P. It starts from position 1 and swings to the furthest
position on the opposite side, position 2. It then oscillates several times with decreasing
amplitude before ending at position 3.

Where does the ball have the most kinetic energy?

A at position 1
B at position 2
C the first time at position 3
D the last time at position 3

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

The cyclist produces the driving force that acts on the back wheel.
In this question, you may ignore any frictional force acting on the front wheel.
(a) The bicycle accelerates until a constant speed is reached.
(i) Describe how the size of the air resistance changes during this time. [2]
(ii) Compare the sizes of the two horizontal forces when the bicycle is accelerating. [1]
(b) 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) the acceleration of the bicycle and the cyclist. [2]
(c) As the bicycle moves, energy is transmitted from the pedals to the back wheel.
Fig. 10.2 shows what happens to the energy input to the pedals.

(i) As energy is transmitted to the back wheel, some is lost. Explain how this happens. [2]
(ii) Calculate the efficiency of the bicycle in transmitting energy from the pedals to the back
wheel. [2]
(d) Some bicycles are made from low density materials. Explain why this is an advantage. [3]

11 When a nucleus of Uranium-235 absorbs a neutron, nuclear fission occurs. In a typical reaction the
total mass decreases by 3 x 10-28 kg.
Given that the speed of light c is 3 x 108 m / s, approximately how much energy is released?
A 9 x 10-20 J B 2 x 10-13 J C 3 x 10-11 J D 3 x 10-5 J

12 Fig. 12.1 shows a children’s ride. A carriage containing children is pulled

up the slope by a motor. The carriage stops at A and then runs down through
B, C and D without further input of energy. Between D and E the carriage
turns through a bend at constant speed. At E, brakes are applied and the
carriage slows to a stop at F. The height of the ride is 30 m at A and 10 m at
C.
 Fig. 11.1
The mass of the carriage and children is 500 kg.
Take the gravitational field strength as 9.8 N/kg.

(a) (i) Discuss the energy changes that occur in the ride from A to D.
(ii) Calculate the maximum potential energy of the carriage and children.
(iii) Assuming that there is no friction between A and C, determine the kinetic
energy of the carriage and children at C. Show your working.
[9]