Question

bob throws a block up into the air, and the block falls back toward the earth. at which point would the kinetic energy be lowest?

Answer 1

The kinetic energy of the block would be lowest at the highest point of its trajectory, right before it starts falling back toward the earth. This is because at this point, the block has just reached its maximum height and is about to change direction, meaning its velocity (and thus kinetic energy) is at its lowest.