Answer the following questions:
$(i)$ State the type of motion shown by a freely falling stone.
$(ii)$ When a stone is thrown vertically upwards,its velocity is continuously decreased. Why?
$(iii)$ Give an example of a motion in which average velocity is zero,but the average speed is not zero.

(N/A) $(i)$ $A$ freely falling stone exhibits uniformly accelerated motion because it is under the influence of constant gravitational acceleration $(g \approx 9.8 \ m/s^2)$.
$(ii)$ When a stone is thrown vertically upwards,the earth exerts a gravitational force on it in the downward direction. This force acts against the direction of motion,causing retardation (negative acceleration),which leads to a continuous decrease in velocity.
$(iii)$ An example of such motion is an object moving in a circular path and returning to its starting point. Since the displacement is zero,the average velocity is zero,but the total distance covered is the circumference of the circle,so the average speed is not zero.