Question

1. In any collision momentum is conserved. Is kinetic energy also conserved? Why?

2.How can one get tired without doing work in the scientific sense?   

3. Which requires more work, to lift a book vertically or to move it over a smooth surface the same distance? Why?

4.Newton times meter per second is equal to a. watt b. kilowatt    c. joule – second    d. kilowatt-hour

5.A coiled spring has    a. potential energy c. no energy b. kinetic energy d. both kinetic and potential energy

6.The more powerful something is the faster it can do work. a. true b. false

7.The unit watt for power is equal to a. Newton per second c. dyne per second    b. Joule per second d. Newton times meter

8. The work done on a body is equal to the change in the ____ of the body. a. power b. energy c. momentum    d. speed

Answer 1

1.

A collision occurs when two or more objects hit each other. When objects collide , each object feels a force for a short amount of time. This force imparts an impulse or change in momentum of each of the colliding objects.

F(t)= P

Since , the duration is very short , t = 0

So P = 0

Hence momentum is conserved in any collision. While kinetic energy is conserved in elastic collision only. Because in inelastic collision , kinetic energy is converted into other forms of energy