Question

Please write in paragraph form details about the phyiscs principles that allow the yo-yo to operate as a toy. (Write about two different principles from two different units).

Answer 1

The yo-yo works on two principles, (i) conservation of energy and (ii) Torque equals the product of Mass moment of Inertia of the disk in yo-yo toy and it's angular acceleration. When you release the yo-yo from the hand,you give some impulse to it which is it's initial rotational kinetic energy.Then as the yo-yo gradually stops it's kinetic energy is stored in the elastic string's potential energy as it unwinds and after it expands and stops, the tension in the string acts as torque which pulls the disk back until the tension in the string becomes zero. But now the disk has some kinetic energy and rolls back to your hand. That's how a yo-yo toy works.