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Question: Two parallel rail tracks run north-south. On one track train A moves north with a speed of 54 km h<s...

Two parallel rail tracks run north-south. On one track train A moves north with a speed of 54 km h-1 and on the other track train B moves south with a speed of 90 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 18 km h-1 with respect to the train A as observed by a man standing on the ground?

A

5ms−15ms^{- 1}

B

10ms−110ms^{- 1}

C

15ms−115ms^{- 1}

D

20ms−120ms^{- 1}

Answer

10ms−110ms^{- 1}

Explanation

Solution

Let the velocity of the monkey with respect to round be VMG.V_{MG}.

Relative velocity of the monkey with respect to train A, VMA=−18kmh−1=−18×518 ms−1=−5 ms−1\mathrm { V } _ { \mathrm { MA } } = - 18 \mathrm { kmh } ^ { - 1 } = - 18 \times \frac { 5 } { 18 } \mathrm {~ms} ^ { - 1 } = - 5 \mathrm {~ms} ^ { - 1 } VMG=VMA+VAG=−5ms−1+15ms−1=10ms−1V_{MG} = V_{MA} + V_{AG} = - 5ms^{- 1} + 15ms^{- 1} = 10ms^{- 1}