State whether the following statements are true or false:
$(a)$ If $\overrightarrow P \cdot \overrightarrow Q = 0$,then the angle between $\overrightarrow P$ and $\overrightarrow Q$ is $0^o$.
$(b)$ If two bodies stick together after a collision,the collision is called an elastic collision.
$(c)$ When an equal force is applied to a heavy and a light object on the same surface,more work is done by the force on the heavy object.

(A-D) False. If $\overrightarrow P \cdot \overrightarrow Q = 0$,the vectors are perpendicular,meaning the angle between them is $90^o$,not $0^o$.
$(b)$ False. If two bodies stick together after a collision,it is called a perfectly inelastic collision,not an elastic collision.
$(c)$ False. Work done is defined as $W = F \cdot d$. If the same force $F$ is applied,the object with less mass will experience higher acceleration $(a = F/m)$ and cover more distance $d$ in the same time interval. Therefore,more work is done on the lighter object.