Physics: A ball is dropped from the top of a building. You choose the top to be the reference level, while ...

1) A ball is dropped from the top of a building. You choose the top to be the reference level, while your friend chooses the bottom. Do the two of you agree on:


a. the ball's potential energy at any point?


b. the change in the ball's potential energy as a result of the fall?


c. the kinetic energy of the ball at any point?





2) Can the kinetic energy of a baseball ever be negative? Please explain without using a formula as this is confusing.





3) Can the gravitational potential energy of a baseball ever be negative? Once again please no formula.





4) If a baseball's velocity is increased to three times its orginial velocity, by what factor does its kinetic energy increase?





5) Can a baseball have kinetic energy and gravitational potential energy at the same time? Explain





6) One athlete lifts a barbell three times as high as another. What is the ratio of changes in potential energy in the two lifts?

Physics: A ball is dropped from the top of a building. You choose the top to be the reference level, while ...
1. A - no. B - yes. C - yes -- at all points.


2. No. Mass is always positive, and the square of a velocity is also always positive.


3. See part 1. But the reference plane is always taken as ground level, so no.


4. Nine.


5. Certainly. Suppose that it has been thrown at the basket, and reaches a height of 12 feet along the way. It reaches the basket which is 10 feet above the floor, and is moving; it has both potential and kinetic energy.


6. Three.