Need Conceptual Physics Help in preparation for test

[nivek114]

Please answer as many as possible! Thanks!

1. If the kinetic energy of a particle is zero, what is its linear momentum?

2. If the speed of a particle is doubled, by what factor is its momentum changed? By what factor is its kinetic energy changed?

3. If two particles have equal kinetic energies, are their momenta necessarily equal? Explain.

4. If two particles have equal momenta, are their kinetic energies necessarily equal? Explain.

5. 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

6. In an isolated system, 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.

7. Explain how linear momentum is conserved when a ball bounces from a floor.

8. Is it possible to have a collision in which all of the kinetic is lost? If so, cite an example.

9. In a perfectly elastic collision between two particles, does kinetic energy of each particle change as a result of the collision?

10. When a ball rolls down an incline, its linear momentum increases. Does this imply that momentum is not conserved? Explain.

11. Consider a perfectly inelastic collision between a car and a large truck. Which vehicle loses more kinetic energy as a result of the collision?

12. Can the center of mass of a body lie outside the body? If so give examples.

13. A sharpshooter 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 is it not as dangerous to be hit by the gun as by the bullet?

14. Early in this century, Robert Goddard proposed sending a rocket to the Moon. Critics took the position that in a vacuum, such as exists between the Earth and the Moon, the gases emitted by the rocket would have nothing to push against to propel the rocket. According to Scientific American (January 1975), Goddard placed a gun in a vacuum and fired a blank cartridge from it. (A blank cartridge fires only the wadding and hot gases of the burning gun powder) What happened when the gun was fired?

15. Does the center of mass of a rocket in free space accelerate? Explain. Can the speed of a rocket exceed the exhaust speed of the fuel? Explain.

 

[tiny-tim]

Please answer as many as possible! Thanks!

he he he

nooo … you start …

try 1 and 2 first. ​

 

[nlightner]

1. If the kinetic energy of a particle is zero, its linear momentum is also zero. This is because kinetic energy is the energy of motion, and if there is no motion, there is no momentum.

2. If the speed of a particle is doubled, its momentum is also doubled. However, its kinetic energy is quadrupled, as kinetic energy is proportional to the square of the velocity.

3. No, their momenta are not necessarily equal. Kinetic energy depends on the mass and velocity of a particle, while momentum only depends on the mass and velocity in a specific direction. Therefore, two particles with equal kinetic energies could have different masses or velocities, resulting in different momenta.

4. Yes, if two particles have equal momenta, their kinetic energies will also be equal. This is because momentum is directly proportional to velocity, and kinetic energy is directly proportional to the square of velocity.

5. Yes, it is possible for parts of an isolated system to be in motion at some later time. This can occur if there is an external force acting on the system, causing it to change its momentum and resulting in parts of the system being in motion.

6. It is possible for both objects to be at rest after the collision, but it is also possible for only one object to be at rest. This would depend on the masses and velocities of the objects before and after the collision. If the two objects have equal masses and velocities in opposite directions, they will both come to rest after the collision. If one object is significantly more massive than the other, it may continue to move after the collision while the lighter object comes to rest.

7. When a ball bounces from a floor, the ball exerts a force on the floor and the floor exerts an equal and opposite force on the ball. This results in a change in momentum for both the ball and the floor, but the total momentum of the system remains constant.

8. Yes, it is possible to have a collision in which all the kinetic energy is lost. An example of this is a completely inelastic collision, where the objects stick together after colliding and come to rest.

9. No, in a perfectly elastic collision, the kinetic energy of each particle does not change. This is because in an elastic collision, both momentum and kinetic energy are conserved.

10. No, the increase in linear momentum of the ball rolling down an incline does not imply that momentum is not conserved