91Ó°ÊÓ

The given data is listed below,

The air resistance is negligible.

This law states that a body will continue to move in a straight line in a uniform motion if no external force acts on that body.

Newton’s first law helps in identifying the forces in the free body diagram of the baseball-bat system and the yo-yo system.

(a)The forces that will act on the baseball if it is considered as the system are force due to the hitting of the bat and the force due to gravity.

The free-body diagram of the baseball and the bat is drawn below

Here, $\stackrel{→}{{\mathrm{F}}_{\mathrm{bat}}}$is the force exerted by the bat on the baseball and $\stackrel{→}{{\mathrm{F}}_{\mathrm{g}}}$is the force due to the gravity

The forces that will act on the baseball if it is considered as the system are force applied for pulling the yo-yo and the force due to gravity.

The free-body diagram of the yo-yo as a system has been drawn below-

Here, $\stackrel{→}{{\mathrm{F}}_{\mathrm{s}}}$is the force needed to pull up the yo-yo and$\stackrel{→}{{\mathrm{F}}_{\mathrm{g}}}$ is force acting downwards due to the acceleration due to gravity.