Elastic and Inelastic Collisions

The law of conservation of momentum states that, 

• p before is less than p after
• p before is the same as p after
• p before is more than p after

When is momentum conserved in a collision?

• When the collision is inelastic.
• When the collision is elastic.
• When the collision is inelastic OR elastic but never an explosion.
• All collisions.

What is the ONLY type of collision where kinetic energy is conserved?

• Elastic

• Inelastic

• Explosions

• Kinetic energy conserved in all collisions

Sally runs and jumps off of a diving board and lands on a tube (she stays in the tube). The collision between Sally and the tube is

• Elastic

• Inelastic

• Explosion

• Completely absurd

Two carts collide. They stick together and continue moving. Is total kinetic energy conserved in this interaction?

• Yes

• No

A dart with a mass of 0.5kg is thrown at 15m/s and sticks into a 1kg apple hanging on a string.  What is the velocity of the dart and apple just after the dart is embedded? 

• 0 m/s
• 5 m/s
• 10 m/s
• 15 m/s

A 35 kg child runs across a store at 4 m/s and jumps onto a 30 kg shopping cart initially at rest. At what speed will the shopping cart and the child move together across the store? 

• 1 m/s
• 2.2 m/s
• 5 m/s
• 6.2 m/s

In an experiment, a toy wooden car with a mass of 0.3 kg, initially at rest, is struck in the rear by a 0.003 kg dart traveling at 15 m/s as shown.  With what speed does the car with the dart stuck in it move after the collision?

• 0.05 m/s
• 0.15 m/s
• 3 m/s
• 10 m/s

Which of the following is true when an object of mass m moving on a horizontal frictionless surface hits and sticks to an object of mass M > m, which is initially at rest on the surface?

• The collision is elastic.

• The momentum of the objects that are stuck together is smaller than the initial momentum of object m.

• The speed of the objects that are stuck together will be less than object m's initial speed.

• The direction of motion of the objects that are stuck together depends on whether the hit is a head-on collision.

An open cart on a level surface is rolling without frictional loss through a vertical downpour of rain. As the cart rolls, an appreciable amount of rainwater accumulates in the cart. The speed of the cart will

• increase because of conservation of mechanical energy
• decrease because of conservation of momentum
• decrease because of conservation of mechanical energy
• remain the same because the raindrops are falling perpendicular to the direction of the cart's motion