Question

A particle moves for 20 s with velocity 3 m/s and then moves with velocity 4 m/s for another 20 s and finally moves with velocity 5 m/s for next 20 s. What is the average velocity of the particle?

• A. 3 m/s
• B. 4 m/s
• C. 5 m/s
• D. Zero

Answer 1

The correct option is B 4 m/s

Key Idea average velocity and instantaneous velocities have same value in a uniform motion. Average velocity is that uniform velocity with which the object will cover the same displacement in same interval of time as it does with actual variable velocity during that time interval.
$=(3m/s\times 20s)+(4m/s\times 20s)+(5m/s\times 20s)$
$=(60+80+100)-240m$
Total time taken $=20+20+20$
$=60s$
$\therefore$ Average velocity $=\frac{240}{60}=4m/s$