Irving, a cat, has a favorite toy that is made up of a squeaky ball at the end of a string. the toy makes up a closed system. irving’s owner dangles the toy so that the ball swings down and then swings back up again.
ignoring any friction, how are kinetic and potential energy related to each other as the ball swings back and forth?

as the ball moves upward, both kinetic and potential energy decrease.
as the ball moves downward, both kinetic and potential energy increase.
as the ball moves upward, kinetic energy decreases and potential energy increases.
as the ball moves downward, kinetic energy decreases and potential energy increases.

As the ball moves upward, kinetic energy decreases and potential energy increases.

Explanation:

In a closed system,  the energy is conserved. It can convert from one form to another. Mechanical energy is the sum of kinetic energy and potential energy.

M.E. = K.E. + P.E.

A body possesses kinetic energy due to virtue of its motion.

K.E. = 0.5 m v²

Potential energy is possessed by a body due to virtue of its position.

P.E. = m g h

The sum of kinetic energy and potential energy remains constant.

K.E. + P.E. = constant

Thus, when the ball moves upwards, potential energy increases thereby decreasing its kinetic energy.

i don't understand. explain it clearly

molecules are free to separate from each other and will take on the shape of the container. molecules move completely at random and high speeds. they vibrate in a fixed position and do not move around much. molecules expand to the edge of their container.