The solution to this problem requires the knowledge of constant angular acceleration motion. The equations used here are similar to those used in constant linear acceleration motion. The detailed solutio is presented in the attachment below.
A boy throws a yo-yo downward and watches it climb back up. As the yo-yo is going down it changes from potential to kinetic in rotational forms.
Rotational kinetic energy is used in the Yo-Yo.
<u>Explanation:</u>
When a boy throws a yo-yo downward its string for a distance h, loses its potential energy in amount and gains kinetic energy in both translational and rotational forms. As it climbs back it loses its kinetic energy and retrieves its potential energy.
In a modern Yo-Yo, the string is not tied to an axle, but loops around it. When Yo-Yo hits the bottom area of its string, a movement of an upward action of force on the axle from the string will stop the descent. Then Yo-Yo spins axle only with rotational kinetic energy.