Question

what is the velocity of a monkey running on the roof of the train A ( moving with velocity $54kh/hr$) against its motion with a velocity of 18 km $h^{-1}$ with respect to the train A as observed by a man standing on the ground?

• A. 5 m $s^{-1}$
• B. 10 m $s^{-1}$
• C. 15 m $s^{-1}$
• D. 20 m $s^{-1}$

Answer 1

The correct option is B 10 m $s^{-1}$

The velocity of money running on the train

The velocity of a monkey with respect to ground is $=-V_M$

The velocity of a monkey with respect to train$A=V_A$

The relative velocity of a monkey with respect to train A $V_{MA}$

$V_{MA}=V_M-V_A$

Given the velocity of a monkey with respect to train A $=V_A=54km/h=15m/s$

And the relative velocity of a monkey with respect to train A

$V_{MA}=-18km/h$

$=-18\times \frac{5}{18}=-5m/s$

Therefore

$V_{MA}=V_M-V_A$

$-5m/s=V_M-15m/s$

$V_M=(-5+15)m/s=10m/s$