CIE A Level Physics

Topic Questions

A LevelPhysicsCIETopic Questions3. Dynamics3.2 Linear Momentum & Conservation

Syllabus Edition

First teaching 2020

Last exams 2024

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3.2 Linear Momentum & Conservation

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11 mark

What is the principle of conservation of momentum?

  • force is equal to the rate of change of momentum

  • momentum is the product of mass and velocity

  • the total momentum of two bodies after collision is equal to their total momentum before collision

  • the total momentum of a system remains constant provided no external force acts on it

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21 mark

The graph shows how the momentum of a motorcycle changes with time.

cie-ial-images114png

What is the resultant force on the motorcycle?

  • 50 N

  • 500 N

  • 2500 N

  • 5000 N

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31 mark

Two bodies travelling in a straight line collide in a perfectly elastic collision. Which of the following statements must be correct?

  • the initial speed of one body will be the same as the final speed of the other body

  • the relative speed of approach between the two bodies equals their relative speed of separation

  • the total momentum is conserved but the total kinetic energy will be reduced

  • one of the bodies will be stationary at one instant

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41 mark

Which row correctly states whether momentum and kinetic energy are conserved in an inelastic collision in which there are no external forces?

 

Momentum

Kinetic energy

A

B

C

D

conserved

not conserved

conserved

not conserved

conserved

conserved

not conserved

not conserved

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51 mark

Which quantity has the same base units as momentum?

  • density × volume × velocity

  • density × energy

  • pressure × area

  • weight ÷ area

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61 mark

Which of the following is a statement of the principle of conservation of momentum?

  • in an elastic collision momentum is constant

  • momentum is the product of mass and velocity

  • the force acting on a body is proportional to its rate of change of momentum

  • the momentum of an isolated system is constant

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71 mark

Two similar spheres, each of mass m and travelling with speed v, are moving towards each other

cie-ial-images115png

The spheres have a head-on elastic collision

Which statement is correct?

  • the spheres stick together on impact

  • the total kinetic energy after impact is m v squared

  • the total kinetic energy before impact is zero

  • the total momentum before impact is 2mv

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81 mark

Trolley X, moving along a horizontal frictionless track, collides with a stationary trolley Y. The two trolleys become attached and move off together.

Which statement about this interaction is correct?

  • some of the kinetic energy of trolley X is changed to momentum in the collision

  • some of the momentum of trolley X is changed to kinetic energy in the collision

  • trolley X loses some of its momentum as heat in the collision

  • trolley X shares its momentum with trolley Y but some of its kinetic energy is lost

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91 mark

A car accelerates from rest. The graph shows the momentum of the car plotted against time.

cie-ial-images116png

What is the meaning of the gradient of the graph at a particular time?

  • the velocity of the car

  • the resultant force on the car

  • the kinetic energy of the car

  • the rate of change of kinetic energy of the car

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101 mark

Which statement about a ball that strikes a tennis racket and rebounds is always correct?

  • total kinetic energy of the ball is conserved

  • total kinetic energy of the system is conserved

  • total momentum of the ball is conserved

  • total momentum of the system is conserved

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11 mark

A wooden block is freely supported on brackets at a height of 4.0 m above the ground, as shown

cie-ial-images128png

A bullet of mass 10.0 g is shot vertically upwards into the wooden block of mass 150 g. It embeds itself in the block. The impact causes the block to rise above its supporting brackets.

 The bullet hits the block with a velocity of 200 m s–1. How far above the ground will the block be at the maximum height of its path?

  • 8.0 m

  • 10.0 m

  • 12.0 m

  • 14.0 m

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21 mark

Two railway trucks of masses m and 5 m move towards each other in opposite directions with speeds 3 u and u respectively. These trucks collide and stick together.

 What is the speed of the trucks after the collision?

  • u over 6

  • fraction numerator 3 u over denominator 6 end fraction

  • u over 3

  • fraction numerator 5 u over denominator 3 end fraction

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31 mark

Sand falls vertically on a conveyor belt at a rate of m kg s–1

cie-ial-images131png

In order to keep the belt moving at constant speed v, the horizontal force that must be exerted is equal to 

  • mv

  • ½ mv

  • mv2

  • ½ mv2

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41 mark

A stationary body explodes into two components of masses m and 3 m.

The components gain kinetic energies X and Y respectively.

cie-ial-images132png

What is the value of the ratio straight x over straight y ?

  • 6 over 1

  • 3 over 1

  • 1 third

  • 1 over 6

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51 mark

A lead pellet of mass 20.0 g is shot horizontally into a stationary wooden block of mass 80.0 g. The pellet hits the block with an impact velocity of 250 m s–1. It embeds itself in the block and it does not emerge.

cie-ial-images133png

After the impact, the block and the pellet continue to move for 8.4 s, how far do they travel in this time?

  • 175 m 

  • 210 m

  • 260 m

  • 525 m

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61 mark

A stationary nucleus has nucleon number A.

 The nucleus decays by emitting a proton with speed v to form a new nucleus with speed u. The new nucleus and the proton move away from one another in opposite directions.

 Which equation gives  in terms of A and u?

  • v equals open parentheses A over 4 minus 1 close parentheses space u

  • v equals open parentheses A minus 1 close parentheses space u

  • v equals A u

  • v equals open parentheses A plus 1 close parentheses space u

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71 mark

A particle X has speed v and collides with a stationary identical particle Y. The collision is perfectly elastic.

 What are the speed and direction of motion of each of the two particles after the collision?

 

 

X

Y

A

stationary

v to the right

B

v over 2  to the right

  v over 2 to the right

C

v over 2  to the left

v over 2  to the right

D

v to the left

stationary

 

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81 mark

The diagram shows two spherical masses approaching each other head-on at an equal speed u. One is of mass m and the other of mass 2 m.

cie-ial-images137png

Which diagram, showing the situation after the collision, is not consistent with the principle of conservation of momentum?

cie-ial-physics-mcq-3-2-q28-diagram-2

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91 mark

An ice-hockey puck slides along a horizontal, frictionless ice-rink surface. It collides inelastically with a wall at right angles to its path, and then rebounds along its original path.

 Which graph shows the variation with time t of the momentum p of the puck?

cie-ial-physics-mcq-3-2-q29

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101 mark

A body, initially at rest, explodes into two masses M1 and M2 that move apart with speeds v1 and v2 respectively.

 What is the ratio  v subscript 1 over v subscript 2 ?

  • M subscript 2 over M subscript 1

  • M subscript 1 over M subscript 2

  • square root of M subscript 2 over M subscript 1 end root

  • square root of M subscript 1 over M subscript 2 end root

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11 mark

A tennis ball of mass 60 g is struck by a tennis racket. The velocity of the ball changes as shown

cie-ial-images118png

What is the magnitude of the change in momentum of the ball?

  • 1.2 × 103 k g space m space s to the power of negative 1 end exponent

  • 4.8 × 103 k g space m space s to the power of negative 1 end exponent

  • 1.2 k g space m space s to the power of negative 1 end exponent

  • 4.8 k g space m space s to the power of negative 1 end exponent

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21 mark

Two spheres approach each other along the same straight line. Their speeds are u subscript 1 and u subscript 2before collision, and v subscript 1and v subscript 2 after collision, in the directions shown below

cie-ial-images119png

Which equation is correct if the collision is perfectly elastic?

  • u1 – u2 = v2 + v1

  • u1 – u2 = v2 – v1

  • u1 + u2 = v2 – v1

  • u1 + u2 = v2 + v1

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31 mark

A lorry of mass 18 tones is travelling at 25.0 m space s to the power of negative 1 end exponent

cie-ial-images120png
A car of mass 800 kg is travelling at 40.0 m space s to the power of negative 1 end exponent towards the lorry.

What is the magnitude of the total momentum?

  • 282 kN s

  • 418 kN s

  • 482 kN s

  • 1222 kN s

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41 mark

The diagram shows the masses and velocities of two trolleys about to collide

cie-ial-images121png

After the impact they move off together

What is the total kinetic energy of the trolleys after the collision?

  • 6.0 J

  • 3.7 J

  • 0.35 J

  • 0.02 J

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51 mark

The diagram shows a cannon ball fired from a cannon

The mass of the cannon is 1600 kg and the mass of the cannon ball is 20 kg

cie-ial-images123png

The recoil velocity of the cannon is 5 m space s to the power of negative 1 end exponenthorizontally

 What is the horizontal velocity of the cannon ball?

  • 100 m space s to the power of negative 1 end exponent

  • 320 m space s to the power of negative 1 end exponent

  • 400 m space s to the power of negative 1 end exponent

  • 8000 m space s to the power of negative 1 end exponent 

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61 mark

A ball of mass 2 kg travelling at ½ m space s to the power of negative 1 end exponent  strikes a ball of mass 3 kg travelling at 

⅓ m space s to the power of negative 1 end exponent.  Both balls are moving along the same straight line as shown

cie-ial-images124png

After collision, both balls move at the same velocity v

What is the magnitude of the velocity v?

  • 1 fifth space m space s to the power of negative 1 end exponent

  • 2 over 5 space m space s to the power of negative 1 end exponent

  • 3 over 2 space m space s to the power of negative 1 end exponent

  • 5 over 2 space m space s to the power of negative 1 end exponent

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71 mark

A molecule of mass m travelling at speed v hits a wall in a direction perpendicular to the wall. The collision is elastic.

What are the changes in the momentum and in the kinetic energy of the molecule caused by the collision?

 

Change in momentum

Change in kinetic energy

A

B

C

D

0

mv

mv2

2mv

0

mv2

0

0

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81 mark

A moving object strikes a stationary object. The collision is inelastic. The objects move off together.

Which row shows the possible values of total momentum and total kinetic energy for the system before and after the collision?

 

Total momentum before collision / kg m s–1

Total momentum after collision / kg m s–1

Total kinetic energy before collision / J

Total kinetic energy after collision / J

A

B

C

D

6

6

6

6

6

6

2

6

90

30

90

90

30

90

30

90

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91 mark

A resultant force of 5 N acts on a body for a time of 4.0 s

Which graph could show the variation with time t of the momentum p of the body?

cie-ial-physics-mcq-3-2-q19

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101 mark

Two train carriages each of mass 7500 kg roll toward one another on a level track. One is travelling at 3.00 m space s to the power of negative 1 end exponent and the other at 1.50 m space s to the power of negative 1 end exponent as shown.

cie-ial-images126png

They collide and join together.

What is the kinetic energy lost during the collision?

  • 4200 J

  • 7500 J

  • 11 250 J

  • 38 000 J

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