Q.
A body begins to walk eastward along a street in front of his house and the graph of his position from home is shown in the following figure. His average speed for the whole time interval is equal to
A) $8\ m/min$
B) $6\ m/min$
C) $\frac{8}{3}\ m/min$
D) $2\ m/min$
Explanation
(b) Average speed is the ratio of distance to time taken
Distance travelled from $0$ to $5s = 40\ m$
Distance travelled from $5$ to $10s = 0\ m$
Distance travelled from $10$ to $15s = 60\ m$
Distance travelled from $15$to $20s = 20$
So, total distance $= 40 + 0 + 60 + 20 = 120\ m$
Total time taken $= 20\ minutes$
Hence, average speed
$= \frac{distance\ travelled\ (m)}{time\ (\min\ )} = \frac{120}{20} = 6\ m/min$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.