Which of the following best represents potential energy being converted to kinetic energy?
1) a roller coaster starts at the top of a hill and then rolls down the hill.
2) a pitcher throws a baseball, and then the batter hits a homerun
3) a man jogs around the block and then stops to drink an energy drink
4) a woman peddles her bicycle across town and back again.

The answer is the roller coaster (A)

Explanation:

Potential energy depends on the height Ep= m*g*h. The more height the system has, more potential energy it owns. Meanwhile it starts to move, the energy transforms from potential (it's going down) to kinetic (it's gaining speed)

Ek = 1/2 * m * v^2

When the roller coaster reaches the ground, all the potential energy has turned into kinetic energy. As it starts going up again, once more the kinetic energy starts to transform into potential energy, due to the system is stoping and gaining height again.

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