5.3 Conservation of Momentum [Mastery check]

In a physics experiment, two carts of mass 1.5 kg each are rolled towards each other.  The orange cart has a velocity of 2 m/s and the blue cart has a velocity of -1m/s.  The carts stick together when they collide.  Calculate their final speed.

• 0.5 m/s
• 1.0 m/s
• 0.33 m/s
• 0.67 m/s

Two football players with mass 75 kg and 100 kg run directly toward each other with speeds of 6 m/s and 8 m/s respectively. If they grab each other as they collide, the combined speed of the two players just after the collision would be:

• 2 m/s 
• 3.4 m/s 
• 4.6 m/s 
• 7.1 m/s

A large box slides across a frictionless surface with a velocity of 12 m/s and a mass of 4 kg,  collides with a smaller box with a mass of 2 kg that is stationary.  The boxes stick together. What is the velocity of the two combined masses after collision?

• 0 m/s
• 4 m/s
• 8 m/s
• 12 m/s

The total momentum before a collision is _________ the total momentum after a collision.

• equal to 
• less than 
• more than
• It depends on the type of collision

The Law of Conservation of Momentum states:

• The total momentum before a collision is equal to the total momentum after a collision.

• The total momentum before a collision is greater than the total momentum after a collision.

• The total momentum before a collision is less than the total momentum after a collision.

• The total momentum before a collision is not related to the total momentum after a collision.

In any collision (crash) the ______ is ALWAYS constant

• Total Momentum
• total speed
• total Velocity
• Energy

A big fish swims upon and swallows a small fish at rest. After lunch, the big fish has less

• momentum
• velocity
• mass

An external force _____ the total momentum of a closed system

• changes

• does not change

An internal force _____ the total momentum of a closed system

• Changes

• does not change

A 10,000 kg railroad car traveling at a velocity of 6 m/s hits a stationary (at rest) boxcar that weighs 5600 kg. At what speed will the second boxcar move if the railroad car reduces its speed to 4.0 m/s after collision?

Assume that all railroad car and the boxcar move in the same direction after the collision.

• 5.0 m/s

• 3.6 m/s

• 7.8 m/s

• 9.8 m/s