Solveeit Logo

Question

Physics Question on Relative Velocity

Two parallel rail tracks run north-south. On one track train AA moves north with a speed of 54kmh154 \,km \,h^{-1} and on the other track train BB moves south with a speed of 90kmh190 \,km\, h^{-1} . what is the velocity of a monkey running on the roof of the train A against its motion with a velocity of 18kmh118 \,km \,h^{-1} with respect to the train AA as observed by a man standing on the ground ?

A

5ms15\,ms^{-1}

B

10ms110\,ms^{-1}

C

15ms115\,ms^{-1}

D

20ms120\,ms^{-1}

Answer

10ms110\,ms^{-1}

Explanation

Solution

Let the velocity of the monkey with respect to ground be vMGv_{MG} . Relative velocity of the monkey with respect to train AA , vMG=18kmh1=18×518ms1=5ms1v_{MG}=-18\,km\,h^{-1}=-18\times\frac{5}{18}\,ms^{-1}=-5\,ms^{-1} vMG=vMA+vAG=5ms1+15ms1=10ms1v_{MG}=v_{MA}+v_{AG}=-5\,ms^{-1}+15\,ms^{-1}=10\,ms^{-1}