A rock is thrown straight up into the air. While it rises and falls, its kinetic energy ...
a
remains constant
b
increases steadily
c
increases then decreases
d
decreases then increases
c) increases then decreases.
As the rock is thrown upward, its kinetic energy is converted to potential energy as it gains height. At the highest point of its trajectory, it has zero kinetic energy and all potential energy. As it falls back down, the potential energy is converted back to kinetic energy, causing its speed and kinetic energy to increase until it reaches the ground again. Therefore, the kinetic energy of the rock increases as it falls back down, but overall it will have a maximum at the top of its trajectory and then decrease again as it falls back down.