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.

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

How is the gravitational force related to the distance between two objects?

If the textbook weighs 19.6 newtons on venus,what is the strength of gravity on venus?