P2 Revision Booklet

Momentum

Easy (Grade D/E)

Q1.          (a)     The diagrams, A, B and C, show the horizontal forces acting on a moving car.
Draw a line to link each diagram to the description of the car’s motion at the moment when the forces act.
Draw only three lines.
 
 	stationary	

                     A	 	
 	constant speed	

                     B	 	
 	slowing down	

                     C	 	
 	accelerating forwards	

(3)

(b)     The front crumple zone of a car is tested at a road traffic laboratory. This is done by using a remote control device to drive the car into a strong barrier. Electronic sensors are attached to a dummy inside the car.

(i)      Draw an arrow in Box 1 to show the direction of the force that the car exerts on the barrier.
(1)

(ii)     Draw an arrow in Box 2 to show the direction of the force that the barrier exerts on the car.
(1)

(iii)    Complete the following by drawing a ring around the correct line in the box.
The car exerts a force of 5000 N on the barrier. The barrier does not move. The force
 
 	more than	 	
exerted by the barrier on the car will be	equal to	5000 N.	
 	less than	 	

(1)

(iv)     Which one of the following gives the most likely reason for attaching electronic sensors to the dummy?
Put a tick () in the box next to your answer.
 
To measure the speed of the car just before the impact.		
To measure the forces exerted on the dummy during the impact.		
To measure the distance the car travels during the impact.		

(1)
(Total 7 marks)
Q2.          The picture shows three skateboarders, A, B and C.

Skateboarder A is not moving.
Skateboarder B is moving towards the ramp at a constant speed.
Skateboarder C is moving on the ramp at a constant speed.
(a)     The skateboarders have different amounts of kinetic energy.
Which two factors affect the kinetic energy of the skateboarders?
Put a tick () in the box next to your answer.
 
direction and mass		
mass and speed		
speed and direction		

(1)

(b)     The skateboarders also have different amounts of momentum.
(i)      Which one of the skateboarders has the smallest amount of momentum?
Draw a ring around your answer.
 
A	B	C	

Give a reason for your answer.
...............................................................................................................
...............................................................................................................
(2)

(ii)     Skateboarder B has a mass of 55 kg.
Use the equation in the box to calculate the momentum of skateboarder B when moving at 4 m/s.
 
momentum    =    mass    ×    velocity	

Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
                          Momentum = .................................................. kg m/s
(2)
(Total 5 marks)
 
Q3.          (a)     A van has a mass of 3200 kg. The diagram shows the van just before and just after it collides with the back of a car.

Before collision	
After collision	

Just before the collision, the van was moving at 5 m/s and the car was stationary.
(i)      Use the equation in the box to calculate the momentum of the van just before the collision.
 
momentum    =    mass    ×    velocity	

Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
                                              Momentum = .............................. kg m/s
(2)

(ii)     The collision makes the van and car join together.
What is the total momentum of the van and the car just after the collision?
                                              Momentum = .............................. kg m/s
(1)

(iii)    Complete the following sentence by drawing a ring around the correct line in the box.
 
 	more than	 	
The momentum of the car before the collision is	the same as	the	
 	less than	 	

momentum of the car after the collision.
(1)

(b)     A seat belt is one of the safety features of a car.

In a collision, wearing a seat belt reduces the risk of injury.
Use words or phrases from the box to complete the following sentences.
decreases	stays the same	increases	

In a collision, the seat belt stretches. The time it takes for the person held by the seat belt to lose momentum compared to a person not wearing a seat belt,
.................................................................................................... .
The force on the person’s body ............................................................................. and so reduces the risk of injury.
(2)
(Total 6 marks)
 Q4.         (a)      (i)     The diagram shows three vehicles travelling along a straight road at 14 m/s.

Which vehicle has the greatest momentum?
                                                   ............................................................
Give the reason for your answer.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)

(ii)     Use the equation in the box to calculate the momentum of the motorbike when it travels at 14 m/s.
 
momentum    =    mass    ×    velocity	

Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
                  Momentum = ............................................................kg m/s
(2)

(b)     The motorbike follows the lorry for a short time, and then accelerates to overtake both the lorry and van.
(i)      Complete the following sentence by drawing a ring around the correct line in the box.
When the motorbike starts to overtake, the kinetic energy
 
 	decreases.	
of the motorbike	stays the same.	
 	increases.	

(1)

(ii)     Give a reason for your answer to part (b)(i).
...............................................................................................................
...............................................................................................................
(1)

(iii)    The graph shows the velocity of the motorbike up to the time when it starts to accelerate. The motorbike accelerates constantly, going from a speed of 14 m/s to a speed of 20 m/s in a time of 2 seconds. The motorbike then stays at 20 m/s.
Complete the graph to show the motion of the motorbike over the next 4 seconds.

(3)
(Total 9 marks)
 Q5.          Motorway accidents have many causes.
(a)     Which one of the following is most likely to increase the chance of a car being in an accident?
Tick () the box next to your answer.
 
The car has just had new tyres fitted.		

The driver has been drinking alcohol.		

A road surface in dry conditions		

Give a reason for your answer.
........................................................................................................................
........................................................................................................................
(2)

(b)     The diagram shows three designs of motorway crash barriers.

Steel sheets	Steel ‘ropes’	Solid concrete	

Before a new design of barrier is used, it must be tested.
A car of mass 1500 kg is driven at 30 m/s to hit the barrier at an angle of 20 degrees.
This barrier must slow the car down and must not break.
Explain why the mass of the car, the speed of the car and the angle at which the car hits the barrier must be the same in every test.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)

(c)     A group of scientists has suggested that new designs of crash barriers should be first tested using computer simulations.
Which two statements give sensible reasons for testing new barrier designs using a computer simulation?
Put a tick () in the box next to each of your answers.
 
The design of the barrier can be changed easily.		

Data for different conditions can be obtained quickly.		

Simulations are more realistic than using cars and barriers.		

(1)
(Total 5 marks)
 
Q6.          (a)     The diagram shows three skiers, X, Y and Z, on a moving chairlift.
The mass of each skier is given in the table.
                             
          Which one of the skiers, X, Y or Z, has the most momentum?
.....................................................................................................................................
          Give the reason for your answer.
.....................................................................................................................................
.....................................................................................................................................
(2)

(b)     At one point in the journey, the chairlift accelerates to a higher speed.
          What happens to the momentum of the three skiers as the chairlift accelerates?
.....................................................................................................................................
(1)
(Total 3 marks)
 Q7.          The diagram shows a child on a playground swing.

(a)     The playground surface is covered in rubber safety tiles. The tiles reduce the risk of serious injury to children who fall off the swing.
          The graph gives the maximum height that a child can fall onto rubber safety tiles of different thicknesses and be unlikely to get a serious head injury.

(i)      Describe how the maximum height of fall relates to the thickness of the rubber safety tile.
...........................................................................................................................
...........................................................................................................................
(1)

(ii)     The maximum height of any of the playground rides is 2 metres.
         What tile thickness should be used in the playground?
...........................................................................................................................
         Give a reason for your answer.
...........................................................................................................................
...........................................................................................................................
(2)

(b)     Use phrases from the box to complete the following sentences.
 
         the force on        the work done to stop  the time taken to stop	

(i)      Falling onto a rubber surface compared to a hard surface increases
         ............................................................ the child.
(1)

(ii)     Momentum is lost more slowly falling onto a rubber surface than on a hard surface.
         This reduces ............................................................ the child.
(1)
(Total 5 marks)
 Q8.          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.

(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	

The total momentum of the two children was ..................................................
(1)
(Total 6 marks)
 Q9.          (a)     The diagram shows a car being driven at 14 rn/s. The driver has forgotten to clear a thick layer of snow from the roof.

          Which of the following has the smallest momentum? Draw a circle around your answer.
          the car                     the driver              the snow
Give a reason for your answer.
....................................................................................................................................
....................................................................................................................................
(2)

(b)     Seeing an obstacle in the road, the driver applies the car brakes. The car slows down in a straight line.
(i)      Does the momentum of the car increase, decrease or stay the same?
..........................................................................................................................
Give a reason for your answer.
..........................................................................................................................
(2)

(ii)     As the car slows down the snow starts to slide. In which direction will the snow start to slide, backwards, forwards or sideways?
..........................................................................................................................
Give a reason for your choice of direction.
..........................................................................................................................
(2)

(c)     Draw a circle around the unit which can be used to measure momentum.
          Nm                J/s                      Ns
(1)
(Total 7 marks)
 Momentum-Mark scheme

M1.(a)      3 lines drawn
all correct
allow 1 mark for each correct line
if two or more lines are drawn from any diagram then all these lines are incorrect

3

(b)     (i)      horizontal arrow to the right 
judge by eye
accept an arrow drawn outside the box if it is labelled correctly
1

(ii)     horizontal arrow to the left
judge by eye
accept an arrow drawn outside the box if it is labelled correctly
1

(iii)    equal to
1

(iv)     to measure the forces exerted on the dummy during the impact
1
[7]

M2.          (a)     mass and speed
1

(b)     (i)      A
reason cannot score if B or C chosen
1

velocity = 0 (m/s)
accept speed for velocity
accept not moving
accept lowest velocity / speed
1

(ii)     220 
allow 1 mark for correct substitution,
ie 55 × 4 provided no subsequent step shown
2
[5]
 M3.         (a)      (i)     16 000
allow 1 mark for correct substitution ie 3200 × 5
2

(ii)     16 000 or their (a)(i)
1

(iii)    less than
1

(b)     increases
1

decreases
correct order only
1
[6]

M4.         (a)      (i)     lorry
reason only scores if lorry chosen
1

greatest mass
accept weight for mass
accept heaviest
accept correct calculations for all 3 vehicles
the biggest is insufficient
1

(ii)     2450
allow 1 mark for correct substitution
ie 175 × 14
2

(b)     (i)      increases
accept any clear indication of the correct answer
1

(ii)     speed increases
accept velocity for speed
accept gets faster
do not accept it accelerates on its own
moves more is insufficient
1

(iii)    straight line going to 6, 20
allow 1 mark for a curve going to 6,20
or a straight line diagonally upwards but missing 6,20
2

horizontal line from 6,20 to 8,20
allow a horizontal line from where their diagonal meets 20m/s to 8,20
1
[9]
 
M5.          (a)     The driver has been drinking alcohol.
reason only scores if this box is ticked
1

driver's reaction time increases
accept slower reactions
accept slower reaction time
orthinking distance / stopping distance increases
do not accept braking distance increases
ordriver less alert
accept driver may fall asleep / be tired
1

(b)     they are all variables that could affect outcome / results
accept specific effect of changing one of the variables
accept to make the test valid
ignore reliable
1

so data / barriers can be compared
accept to see which is / works best / safest
do not accept fair test on its own
1

(c)     ticks in both the top and middle boxes
1
[5]
 M6.          (a)     Y
accept the one in the middle
accept 90
1
          has the biggest mass
reason does not score if X or Z is chosen
accept weight for mass
accept weighs the most
accept they are the heaviest
accept has a larger mass
do not accept weighs 90kg’s on its own
biggest/larger on its own is not sufficient
1

(b)     increases
1
[3]
 M7.          (a)     (i)      the thicker the tile, the greater the(fall) height
accept the higher (the fall) the thicker the tile
accept there is a positive correlation
do not accept they are proportional
1

(ii)     60 (mm)
accept any number or range between 60 and 85 inclusive
if units are given must match range
1
         (minimum thickness) needed to reduce risk of injury
reason must match thickness choice
do not accept to keep child safe
accept an answer in terms of – the thicker the tile, the less chance there is of a serious injury if the answer given is greater than 60
accept answers in terms of use of graph e.g. the graph shows that for a 2m fall a thickness of 60 mm is needed
minimum level answer’ the graph shows that’s what’s needed’ accept only if 60 is the answer
1

(b)     (i)      the time taken (to stop)
1
(ii)     (the) force (on)
1
[5]
M8.          (a)     (i)      mass
do not accept weight
1
         speed
accept velocity
answers can be in either order
1
(ii)     zero
accept nothing
1

(b)     (i)      100
allow 1 mark for correct substitution of data
2
(ii)     conserved
1
[6]
 M9.          (a)     the snow
1
smallest mass
do not accept it is not moving
accept weight for mass
accept it’s the lightest
1

(b)     (i)      decrease
1
velocity reducing
accept speed for velocity
accept it is stopping
do not accept the brakes are on
accept car is decelerating
1

(ii)     forwards
1
         direction of momentum does not change 
or the car stops and snow does not
dependent on forwards given
accept answers given in terms of Newton’s second or first law of motion
accept momentum of snow
do not accept the snow still has momentum
1

(c)     Ns
1
[7]