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GCSE Physics revision – P2 – Quarter 1 - Forces

1. The picture shows two children, X and Y, skating towards each other at an ice rink.

The children collide with each other, fall over and stop.

X

M a ss = 4 0 k gVe loc ity = 2 .5 m /s

Y

M a ss = 5 0 k gVe lo c ity = 2 m /s

(a) Before the collision the children had different amounts of kinetic energy.

(i) What are the two factors that determine the kinetic energy of the children?

1 ........................................................................................................................

2 ........................................................................................................................(2)

(ii) What was the total kinetic energy of the children after they had fallen over and stopped?

...........................................................................................................................(1)

(b) The total momentum of the children before and after the collision is zero.

(i) Use the equation in the box and the data given in the diagram to calculate the momentum of child Y before the collision.

momentum = mass ×velocity

Show clearly how you work out your answer.

...........................................................................................................................

...........................................................................................................................

Momentum = ............................................... kg m/s(2)

(ii) Complete the following sentence using one of the words in the box.

conserved decreased increased

Hinchley Wood School and 6th Form Centre 1


The total momentum of the two children was ..................................................(1)

(Total 6 marks)

2. The lorry, the car and the motor cycle are travelling along a straight road in the direction shown.

All three vehicles are travelling at the same speed.

overhead view

(a) Which word is used to describe the speed of an object in a particular direction?

....................................................................................................................................(1)

(b) Which of the three vehicles will have the greatest momentum?

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Explain your answer

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....................................................................................................................................(4)

(c) Complete the sentences.

(i) When a vehicle has a steady speed the frictional forces ..................................the driving force.

(ii) Momentum has both .................................................... and direction.(2)

(Total 7 marks)

3. (a) The diagram shows a car travelling at a speed of 12 m/s along a straight road.

(i) Use the equation in the box to calculate the momentum of the car.



momentum = mass × velocity

Mass of the car = 900 kg

Show clearly how you work out your answer.

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Momentum = .............................. kg m/s(2)

(ii) Momentum has direction.

Draw an arrow on the diagram to show the direction of the car’s momentum.(1)

(b) The car stops at a set of traffic lights.

How much momentum does the car have when it is stopped at the traffic lights?

.....................................................................................................................................

Give a reason for your answer.

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.....................................................................................................................................(2)

(Total 5 marks)

4. Part of a bus route is along a high street.The distance – time graph shows how far the bus travelled along the high street and how long it took.



(a) The bus travels the slowest between points D and E.

How can you tell this from the graph?

.....................................................................................................................................

.....................................................................................................................................(1)

(b) Between which two points was the bus travelling the fastest?

Put a tick ( ) in the box next to your answer.

Points

A – B

B – C

C – D(1)

(c) There is a bus stop in the high street.This is marked as point B on the graph.

(i) What is the distance between point A on the graph and the bus stop?

Distance .............................. metres(1)



(ii) How long did the bus stop at the bus stop?Show clearly how you work out your answer.

...........................................................................................................................

Time = .............................. seconds(2)

(d) A cyclist made the same journey along the high street.The cyclist started at the same time as the bus and completed the journey in 200 seconds. The cyclist travelled the whole distance at a constant speed.

(i) Draw a line on the graph to show the cyclist’s journey.(2)

(ii) After how many seconds did the cyclist overtake the bus?

The cyclist overtook the bus after .............................. seconds.(1)

(Total 8 marks)

5. (a) The diagrams below show pairs of forces acting on different objects. In each case describe what happens when the forces are increased. Then describe what happens when the forces are removed.

(i)

P u ll in g fo rc eP u ll in g fo rc e

T h in s tr ip o f p la s t ic in e

When the forces are increased

...........................................................................................................................

...........................................................................................................................

When the forces are removed

...........................................................................................................................

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(ii)

P u sh in g fo rc eP u s h in g f o rc e

S tro n g m e ta l sp r in g


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(iii)

P u sh in g fo rc e P ush in g fo rce

T h in p las tic ru le r


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...........................................................................................................................


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(b) The graph shows the increase in length of a spring against load (force).

11

1 0

9

8

7

6

5

4

3

2

1

00 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0

L o ad o n sp rin g (N )

In crease inlen g th o fsp rin g (c m )



The length of the spring with no load was 15 cm. Use the graph to find:

(i) The load needed to produce an increase in length of 2 cm.

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(ii) The increase in length produced by a load of 2.3 N.

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(iii) The length of the spring when the load was 2.3 N.

...........................................................................................................................(3)

(Total 9 marks)

6. A small object falls out of a balloon.

Choose words from the list to complete the sentences below.

friction gravity air pressure

accelerates falls at a steady speed slows down

The weight of an object is the force of ............................................ which acts on it.

When you drop something, first of all it ............................................... .

The faster it falls, the bigger the force of ........................................... which acts on it.

Eventually the object ............................................. .(Total 4 marks)

7. (a) A driver may have to make an emergency stop.

Stopping distance = thinking distance + braking distance.

Give three different factors which affect the thinking distance or the braking distance. In your answer you should explain what effect each factor has on the stopping distance.

1. ................................................................................................................................

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2. ................................................................................................................................



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3. ................................................................................................................................

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(b) Complete the following sentences by writing in the two missing words.

Acceleration is the rate of change of .............................................................. .

The acceleration of a car depends on the force applied by the engine and the

........................................... of the car.(2)

(c) A car moves because of the force applied by the engine.

Name two other forces which act on the car when it is moving. Give the direction in which each of these factors acts.

1. Name of force ........................................................................................................

Direction of this force ...........................................................................................

2. Name of force ........................................................................................................

Direction of this force ........................................................................................... (4)

(d) Complete the following sentence by writing in the missing word.

The velocity of a car is its speed in a particular .......................................................(1)

(Total 13 marks)

8. A cyclist accelerates from a set of traffic lights.

The driving force of the back tyre on the ground is 250 N.

(a) How much work is done by this force when the cyclist travels 5 metres?(Show your working.)

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Answer ............................ joules (J)



(2)

(b) What happens to the energy transferred by this force?

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.....................................................................................................................................(2)

(Total 4 marks)

9. The graph shows the speed of a runner during an indoor 60 metres race.

sp eed(m e tres p e r

seco n d )

tim e (sec on d s )

1 0

5

00 2 4 6 8 1 0

A

B

C

(a) Choose words from this list to complete the sentences below.

moving at a steady speed slowing down

speeding up stopped

Part A of the graph shows that the runner is .............................................................

Part B of the graph shows that the runner is .............................................................

Part C of the graph shows that the runner is .............................................................(3)

(b) Calculate the acceleration of the runner during the first four seconds.(Show your working.)

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....................................................................................................................................(3)

(Total 6 marks)

10. When you slide a book across a table, there is a force of friction between the book and the table.



(a) Which arrow shows the force of friction that acts on the book? ...............................(1)

(b) The force of friction will slow the book down.Write down one other effect that the force of friction will have on the book.

....................................................................................................................................(1)

(Total 2 marks)

11.

In a science lesson, some children float an apple on some water.

One of the children says:

“The apple is not moving. That means that there cannot be any forces acting on it.”

Do you agree?Explain your answer as fully as you can.

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...............................................................................................................................................(Total 3 marks)

12. The manufacturer of a family car gave the following information: Mass of car 950 kg.

The car will accelerate from 0 to 33 m/s in 11 seconds.

(a) Calculate the acceleration of the car during the 11 seconds

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Answer .............................................................(2)



(b) Calculate the force needed to produce this acceleration.

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.....................................................................................................................................(3)

(c) The manufacturer of the car claims a top speed of 110 miles per hour. Explain why there must be a top speed for any car.

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.....................................................................................................................................(3)

(Total 8 marks)

13. When a gun is fired, a very large force acts on the bullet for a very short time.

The change in momentum of the bullet is given by the following relationship:

force (N) × time(s) = change in momentum (kg m/s)

(a) An average force of 4000 newton acts for 0.01 seconds on a bullet of mass 50g.

Calculate the speed of the bullet. (Show your working.)

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Answer ............................................... m/s(4)

(b) The bullet is fired horizontally. In the short time it takes for the bullet to reach its target, its horizontal speed has fallen to 80% of its initial speed.

(i) Explain why the speed of the bullet decreases so quickly.

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...........................................................................................................................(2)

(ii) Calculate the percentage of its original kinetic energy the bullet still has when it reaches its target.

(Show your working.)

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...........................................................................................................................(4)

(Total 10 marks)

14. The diagram shows a high jumper.

In order to jump over the bar, the high jumper must raise his mass by 1.25m.The high jumper has a mass of 65kg. The gravitational field strength is 10N/kg.

(a) The high jumper just clears the bar.

Use the following equations to calculate the gain in his gravitational potential energy.

w e ig h t(n e w to n , N )

m a ss(k ilo g r a m , k g )

g ra v ita tio n a l f ie ld s tren g th(n ew to n /k ilo gr a m , N /k g )

= ×

w e ig h t(n e w to n , N )

c h a n g e in v er tica l h e ig h t(m e tre , m )

ch a n g e in g ra v ita tio n a l p o ten tia l en er g y(jo u le , J )

= ×

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Gain in gravitational potential energy .................... J(4)

(b) Use the following equation to calculate the minimum speed the high jumper must reach for take-off in order to jump over the bar.

](m/s),cond)[(metre/sekg)(kilogram,J)(joule,

[speed]×mass×21

=energykinetic

22

2

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Speed .................... m/s(3)

(Total 7 marks)

15. (a) The amount of damage caused when a car collides with a wall depends on the amount of energy transferred.

If the speed of a car doubles, the amount of energy transferred in a collision increases four times.

Explain, as fully as you can, why this is so.

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.....................................................................................................................................(3)

(b) The diagram shows a car and a lorry about to collide.

speed = 20km/h

speed = 40km/h

0.5 tonne

9.5 tonne

When they collide, the two vehicles become tightly locked together.

(i) Calculate the speed of the vehicles immediately after the collision.

(Show your working. There is no need to change to standard units.)

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Answer ....................................... km/h(6)

(ii) The collision between the car and the lorry is inelastic.

Explain, in terms of energy, what this means.



...........................................................................................................................(1)

(Total 10 marks)

16. The drawing shows an investigation using a model steam engine to lift a load.

In part of the investigation, a metal block with a weight of 4.5 N was lifted from the floor to a height of 90 cm.

(a) Explain what causes the weight of the metal block.

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.....................................................................................................................................(2)

(b) (i) What is the tension in the string when the block is lifted at a steady speed?

...........................................................................................................................(1)

(ii) Explain your answer to part (b) (i).

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...........................................................................................................................(1)

(c) (i) Calculate the work done in lifting this load. Write the equation you are going to use, show clearly how you get to your answer and give the unit.

Equation ...........................................................................................................

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Work = ..............................................(3)



(ii) How much useful energy is transferred to do the work in part (c) (i)?

...........................................................................................................................(1)

(d) In another part of the investigation, 250J of work is done in one minute. Use the equation:

power = takentimedonework

to work out the useful power output. Give the unit.

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Power = ...............................(2)

(Total 10 marks)

17. A rollercoaster car stops above a vertical drop. Suddenly it falls under gravity.

The drop is 60 metres high and at the bottom of the drop the car travels at 125 km/h.The acceleration experienced by the people in the car is 10 m/s2. The mass of the car and itspassengers is 1210 kg.

Calculate the force exerted on the car and its passengers. Show your working.

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Force = ........................... N(Total 3 marks)

18. (a) How can the momentum of an object be calculated?

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.....................................................................................................................................(2)

(b) In a collision momentum is always conserved. What does this mean?

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.....................................................................................................................................(2)

(c) Two trolleys are placed on a frictionless runway as shown in the diagram below. Trolley A has a protruding pin, and trolley B is fitted with a piece of soft cork so that the trolleys will stick together after colliding.

frictionless runway

pin cork

A B

Trolley A has a mass of 2 kg, and trolley B has a mass of 1 kg. Trolley B is stationary. Trolley A strikes trolley B at a speed of 6 m/s. Both trolleys then move to the right together.

(i) Calculate the speed at which trolleys A and B jointly move after the collision.

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...........................................................................................................................(4)

(ii) Calculate the change in kinetic energy which occurs during the collision.

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...........................................................................................................................(4)

(Total 12 marks)


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