a train is moving towards east with a speed of 20m/s . A person is running on the roof of the train with a speed 3m/s against the motion of train . Velocity of the person as seen by an observer on ground will be-

Ans is 17m/s towards east..how?

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Solution

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Velocity of the train wrt observer on ground= 20m/s east

Velocity of the person = 3m/s west

Relative velocity of person with respect to an observer on ground = 20 - 3 = 17 m/s

This is because , for an observer on a ground , the person is on the train which moving. The frame on which person is running moving towards the east . So,the velocity of man with respect to train is 3 m/s (west).
Train moves 20 m/ss wr ground .
Wrt ground the person is moving west with 3m/s on a frame (train) which is moving 20m/s east .
For relative velocity of person wrt ground , we have to consider the velocity man (3m/s west) and velocity of frame (20m/s east ). Hence net velocity,
3-20 = -17 m/s
the negative sign indicates that the motion towards east.

The observer will see the person moving towards west only if , the velocity of the man is more than the velocity of the frame on which he moves that is more than 20 metre per second here

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a train is moving towards east with a speed of 20m/s . A person is running on the roof of the train with a speed 3m/s against the motion of train . Velocity of the person as seen by an observer on ground will be- Ans is 17m/s towards east..how?

a train is moving towards east with a speed of 20m/s . A person is running on the roof of the train with a speed 3m/s against the motion of train . Velocity of the person as seen by an observer on ground will be-

Ans is 17m/s towards east..how?