Q.
A cyclist starts from the centre $O$ of a circular park of radius one kilometre, reaches the edge $P$ of the park, then cycles along the circumference and returns to the centre along $QO$ as shown in figure. If the round trip takes ten minutes, the net displacement and average speed of the cyclist (in metre and kilometre per hour) is
A) $0,\ 1$
B) $\frac{\pi + 4}{2},\ 0$
C) $21.4,\frac{\pi + 4}{2}$
D) $0,\ 21.4$
Explanation
(d) Net displacement $= 0$ and total distance $= OP + PQ + QO$
$= 1 + \frac{2\pi \times 1}{4} + 1 = \frac{14.28}{4}\ km$
Average speed$\ = \frac{14.28}{4 \times 10/60}$
$= \frac{6 \times 14.28}{4} = 21.42\ km/h$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.