Physics homework help? 1. An isolated system is initially at rest. Is it possible for parts of the system to be in motion at some later time? If so, explain how this might occur. 2. If two objects collide and one is initially at rest, is it possible for both to be at rest after the collision? Is it possible for one to be at rest after the collision? Explain. 3. Explain how linear momentum is conserved when a ball bounces from a floor. 4. A ball of clay is thrown against a brick wall. The clay stops and sticks to the wall. Is the principle of conservation of momentum violated in this example? 5. You are standing perfectly still and then you take a step forward. Before the step your momentum was zero, but afterward you have some momentum. Is the principle of conservation of matter violated in this case? 6. When a ball rolls down an incline its linear momentum increases. Is the principle of conservation of momentum violated in this process? 7. A sharp shooter fires a rifle while standing with the butt of the gun against his shoulder. If the forward momentum of a bullet is the same as the backward momentum of the gun, why isn't it as dangerous to be hit by the gun as by the bullet? 8. A large bed sheet is held vertically by two students. A third student, who happens to be the star pitcher on the baseball team, throws a raw egg at the sheet. Explain why the egg does not break when it hits the sheet, regardless of its initial speed. 9. A skater is standing still on a frictionless ice rink. Her friend throws a Frisbee straight at her. In which of the following cases is the largest momentum transferred to the skater? A) the skater catches the Frisbee and holds onto it. B) The skater catches the Frisbee momentarily but then drops it vertically downward. C) the skater catches the Frisbee holds it momentarily and throws it back to her friend. 10. A raw egg dropped to the floor breaks upon impact. However, a raw egg dropped onto a thick foam rubber cushion from a height of about 1 m rebounds without breaking. Why is this possible? 11. Early in the 20th century Robert Goddard proposed sending a rocket to the moon. Critics objected that in a vacuum such as exists between Earth and the moon, the gases emitted by the rocket would have nothing to push against to propel the rocket. According the Scientific American, Goddard placed a gun in a vacuum and fired a blank cartridge from it.What happened when the gun was fired? 12. If you throw a ball horizontally while standing on roller skates you roll backwards with a momentum that matches that of the ball. Will you roll backward if you go through the motions of throwing the ball but instead hold on to it? Explain. 13. Light consists of tiny 'corpuscles' called photons that possess momentum. This can be demonstrated with a radiometer. Metal vanes painted black on one side and white on the other are free to rotate around the point of a needle mounted in a vacuum. When photons are incident on the black surface they are absorbed; when photons are incident upon the white surface they are reflected. Upon which surface is the impulse of incident light greater and which way will the vanes rotate?