Which is an example of the conversion of gravitational potential energy into kinetic energy? a sliding hockey puck an idling car a swimming fish a falling raindrop

A falling raindrop.

The reason why it's because mass of a raindrop is under influence of gravity pushing it down towards earth surface. When it hit the surface kinetic energy is released.

Explanation:

Kinetic energy depends on the mass and the velocity of an object.

Potential energy depends on the mass of an object an how high it is.

A raindrop initially has potenial energy because of its high above the ground, when is falling it has a velocity, and having a velocity means it now has kinetic energy.

By falling, the raindrop exchange potential energy for kinetic energy, as it falls, its potential energy is lower since it is at a lower altitud.

And also when it falls it accelerates towards the ground wich makes it have grater velocity and by analogy greater kinetic energy.

grav potential energy

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.