Can u help me out?

Question

In which of the following occurences is potential energy being transform into kinetic? Explain.

a.) a man climbing a post
b.) a battery operated toothbrush
c.) a baseball thrown vertically upward
d.) a pring controlled door that is suddenly pushed open
e.) a swimmer jumping up and down on a diving board

Answer 1

This is very long time ago, but I'll give it a try.
e.) When the swimmer stand on the board he will build up potential energy in the board by pushing his legs down. Then this potential energy in the board helps the swimmer to get pushed upwards. When he is in it's highest position in the air, the moment he has no more speed the potential energy in the swimmer is highest. When he falls back to the board, the potential energy is converted into kinetic energy. This kinetic energy is converted into potential energy in the board again when the swimmer touches the board again, etc, etc.
Btw. Not all energies are completely converted from potential to kinetic energy and vv. because there's friction in the board and in the air-resistance.

comments in answer d.) I think this is not the right one.
The door is closed by a spring. There is possibly still some tension in the spring when the door is in closed position, but this doesn't really matter, because when you open the door, the spring tension increases. Only when the spring closes the door again, the potential energy in the spring is converted into kinetic energy, so not when it is opened. The potential energy in the spring increases with the tension that's build up in it.

Answer 2

d) the spring controlled door is potential until whoever is pushing it open lets go and then it forms kinetic energy as it swings itself shut

Answer 3

I would have to say D. The spring isn't moving until it's released. Of course, it's been a few years since I sat in a physics class. :)

Answer 4

I'll go for Option D