$A$ person is running along a circular path in a park.
$(a)$ At what point does he change his direction while running?
$(b)$ If he covers half of the circular path,what will be his displacement? Draw a diagram showing it.

(N/A) In circular motion,the direction of motion changes at each and every point along the path because the velocity vector is always tangent to the circle at any given point.
$(b)$ Displacement is the shortest distance between the initial and final positions. If a person starts at point $A$ and covers half of the circular path to reach point $B$,the displacement is the straight-line distance between $A$ and $B$,which is equal to the diameter of the circle $(2r)$.
Diagram: The image shows a circle with points $A$ and $B$ at opposite ends of a diameter,with the radius $r$ indicated from the center to point $B$. The displacement is the straight line $AB = 2r$.