A2L Item 159
- Description: Identify the final velocity after a totally inelastic collision.
- Goal: Explore momentum concepts
- Source: CT151.2S02-44
- Keywords: Conservation, Interactions, Mechanics, Momentum
The question for students:
A cart
of mass 2m collides and sticks to a cart of mass m that is initially at
rest. What is the speed of the combination after the collision?
- v
- 2v/3
- v/3
- 0
- None of the above.
- Cannot be determined.
Commentary for teachers:
Answer
(2) This question is useful for probing pre-existing ideas about momentum, and also for distinguishing momentum ideas from kinetic energy. It should be used just after, or even before, covering momentum concepts.
Usually students starting momentum already have had some energy, and kinetic energy in particular. If appropriate, they can be asked if energy is lost in the collision. Is more or less energy lost if the carts do not stick together?