Chan Hee is inflating a basketball using an air pump. He notices that the pump gets warm as he uses it. What is a good hypothesis that could lead to new experimentation?

If there is no air in a basketball, then it is hard to play the game.
A basketball that is inflated bounces better than one that is not inflated.
If air in a pump is squeezed more, then the air gets hotter because energy is added to it.
Basketball is more fun to play than baseball because you have to move a lot more.

Assume that two of the electrons at the negative terminal have attached themselves to a nearby neutral atom. there is now a negative ion with a charge -2e at this terminal. what are the electric potential and electric potential energy of the negative ion relative to the electron? the electric potential and the electric potential energy are both twice as much. the electric potential is twice as much and the electric potential energy is the same. the electric potential is the same and the electric potential energy is twice as much. the electric potential and the electric potential energy are both the same. the electric potential is the same and the electric potential energy is increased by the mass ratio of the oxygen ion to the electron. the electric potential is twice as much and the electric potential energy is increased by the mass ratio of the oxygen ion to the electron.

What is the efficiency of an engine that does 80 j of work and exhausts 320 j of heat while taking in 400 j of heat ? a. 10% b. 20% c. 80% d. 25%

How many excess electrons must be present on each sphere if the magnitude of the force of repulsion between them is 4.57×10−21 newtons?