$A$ body thrown in the vertically upward direction rises up to a height $h$ and comes back to the position of its start. Calculate: $(a)$ the total distance travelled by the body and $(b)$ the displacement of the body. Under what condition will the magnitude of the displacement be equal to the distance travelled by an object?

(N/A) Since the body travels a distance $h$ upwards and $h$ downwards,the total distance travelled is $h + h = 2h$.
$(b)$ As the body returns to its starting point,the displacement is $0$.
The magnitude of the displacement is equal to the distance travelled if the object moves along a straight line in a single direction without changing its direction.