Physics Review: Energy and Collisions

A runner has a momentum of 670 kg m/s and is traveling at a velocity of 9 m/s. What is his mass?

• 6030 kg
• 0.0134 kg
• 74.4 kg
• 80 kg

A boy kicks a football with a force of 20 N, the time the force acts for is 0.3 s. Calculate the impulse on the ball.

• 1 N⋅s

• 6 N⋅s

• 33.3 N⋅s

The difference between a car hitting a wall vs. a car hitting a hay stack is

• the Impulse on the car hitting the wall is greater
• the change in momentum of the car hitting the wall is greater
• the force on the car hitting the hay stack is greater
• the collision time of the car hitting the hay stack is greater

How fast does a 50 kg person need to move to have the same momentum as a 1000 kg car moving at 1m/s?

• 1 m/s
• 100 m/s
• 2 m/s
• 20 m/s

Two skaters of different masses initially at rest push off of each other. How do their momentums after compare?

• Heavy is higher

• Equal but opposite directions

• Light is higher

• no way to tell

Two skaters of different masses initially at rest push off of each other. How do their velocities after compare?

• Heavy is higher

• Equal but opposite directions

• Light is higher

• no way to tell

Two cars of equal mass and collide and bumpers stick together. What type of collision is this?

• Elastic
• Inelastic
• Expensive

In an Inelastic collision what is NOT conserved?

• Kinetic Energy
• Momentum
• Both kinetic energy and momentum are conserved in inelastic

What is the speed of the first ball after the collision?

• 4.2 m/s

• 27 m/s

• 42 m/s

• 69 m/s

A 10kg toy truck moves at 5m/s East. It collides and bounces off of a 5kg toy car moving 10 m/s moving west. Which equation would you use to solve for the final velocity of the car?

• m₁v_1i+m₂v_2i=m₁v_1f+m₂v_2f
  
• (m₁+m₂₎v_i=m₁v_1f+m₂v_2f 
• m₁v_1i+m₂v_2i=(m₁+m₂)v_f