Momentum MCQs (set 5)

The graph shows the variation with time, t, of the force, F, acting on a body. What physical quantity does the area X represent?

• the displacement of the body

• the work done on the body

• the change in momentum of the body

• the rate of change of kinetic energy of the body

• the rate of change in momentum of the body

Two ice skaters, initially at rest and in contact, push apart from each other. Which line, A to D, in the table states correctly the change in (1) the total momentum and (2) the total kinetic energy of the two skaters?

• (1) unchanged,

  (2) increases

• (1) unchanged,

  (2) unchanged

• (1) increased,

  (2) increases

• (1) increased,

  (2) unchanged

A gas molecule of mass m in a container moves with velocity v. It makes an elastic collision at right angles to the walls of the container. What is the magnitude of the change in momentum of the molecule?

• zero

• ½mv²

• mv

• 2mv

The diagram shows a strobe photograph of a mark on a trolley X, moving from right to left, in collision with another trolley Y which had no mark on it. After the collision both trolleys are in motion together. Which one of the following is consistent with the photograph?

• Trolley Y has the same mass as trolley X and was initially stationary.

• Trolley Y had a smaller mass than X and was moving from right to left.

• Trolley Y had the same mass and was initially moving left to right at the same speed as trolley X.

• Trolley Y had the same mass and was initially moving left to right at a higher speed than trolley X.

A body is accelerated from rest by a constant force. Which one of the following graphs best represents the variation of the body’s momentum p with time t?

• 
• 
• 
• 

Take the acceleration due to gravity, ge, as 10 m·s−2 on the surface of the Earth. The acceleration due to gravity on the surface of the Moon is ⅙ge. An object whose weight on Earth is 5.0 N is dropped from rest above the Moon’s surface. What is its momentum after falling for 3.0 s?

• 2.5 kg·m·s−1

• 6.2 kg·m·s−1

• 15 kg·m·s−1

• 25 kg·m·s−1

A body X moving with a velocity v makes an elastic collision with a stationary body Y of equal mass on a smooth horizontal surface.

• velocity of X: v/2, velocity of Y: -v/2

• velocity of X: -v/2, velocity of Y: v/2

• velocity of X: v, velocity of Y: 0

• velocity of X: 0, velocity of Y: v

The diagram shows the graph of force on a car against time when the car of mass 500 kg crashes into a wall without rebounding.

• The area under the graph is equal to the initial momentum of the car.

• Momentum is not conserved in the collision.

• Kinetic energy is conserved in the collision.

• The average force exerted on the car is 10 × 10^4 N.

The graph shows how the force acting on a body changes with time. The body has a mass of 0.25 kg and is initially at rest. What is the speed of the body after 40 s, assuming no other forces are acting?

• 200 m·s⁻¹

• 400 m·s⁻¹

• 800 m·s⁻¹

• 1600 m·s⁻¹

A stationary unstable nucleus of mass M emits an α-particle of mass m with kinetic energy E. What is the speed of recoil of the daughter nucleus V?

• V = √(2mE / (M - m))

• V = √(2mE / M)

• V = (M - m) / √(2mE)

• V = 2mE / (M - m)²