Momentum Review

A freight car of mass 20,000kg moves along a frictionless level railroad track with a constant speed of 15m/s. What is the momentum of the car?

• 30,000 kgm/s

• 3,000kgm/s

• 1,333.3kgm/s

• 300,000kgm/s

A 5000kg sailboat moves with a momentum of 15,000kgm/s, what is the velocity of the boat?

• 3m/s

• 3m/s/s

• 0.33m/s

• 0.33m/s/s

A cannon fires a cannonball and recoils backwards. Which of the following statements is true about the cannon recoil?

• It happens because the energy of the system is conserved.

• It happens because the energy of the system is increased.

• It happens because the momentum of the system changes.

• It happens because the momentum of the system is conserved.

What is the momentum of the cannon after firing a cannon ball, giving the ball an initial momentum of 5,000kgm/s to the right?

• 5,000kgm/s to the right

• 5,000kgm/s to the left

• 0kgm/s

A platform moves at a constant velocity on a horizontal surface. What happens to the velocity of the platform after a sudden heavy rain falls, increasing the mass of the platform?

• It increases because energy is conserved.

• It decreases because energy is conserved.

• It remains constant because the momentum is conserved.

• It increases because momentum is conserved.

• It decreases because momentum is conserved.

A stationary skateboarder I with a mass of 50kg pushes a stationary skateboarder II with a mass of 75kg. After the push skateboarder II moves with a velocity of 2m/s to the right, what is the velocity of the skateboarder I?

• 3m/s to the left

• 2m/s to the left

• 1m/s to the right

• 2m/s to the right

• 3m/s to the right

A loaded freight car A with a mass of 24,000kg moves at a constant velocity of 8m/s on a horizontal railroad track and collides with an empty stationary car B with a mass of 8,000kg. After the collision the cars stick to each other and move like one object, what is the velocity of the two cars after the collision?

• 2m/s

• 4m/s

• 6m/s

• 8m/s

• 12m/s

A 40 kg skateboarder runs at a constant velocity of 12 m/s and jumps on a stationary skateboard with a mass of 8 kg. What is the velocity of the skateboard+skater after the jump?

• 12m/s

• 90m/s

• 60m/s

• 20m/s

• 10m/s

An 80 kg diver jumps off a moving boat. The boat and diver have a combined mass of 480 kg and moves at a constant velocity of 2 m/s. What is the velocity of the boat after the jump if the diver jumps off the back of the boat with a velocity of 3 m/s in the opposite direction to the initial velocity of the boat?

• 2m/s

• 3m/s

• 4m/s

• 5m/s

• 6m/s

Block A with a mass 2m moves on a frictionless horizontal surface at a constant speed v and collides inelastically with B of mass m. What is the velocity of two blocks after the collision?

• v

• 1/2v

• 1/3v

• 2/3v

• 1/4v