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An escalator is moving downwards with a ...

An escalator is moving downwards with a uniform speed u. A man of mass m is running upwards on it at a uniform speed `upsilon`. If the height of the escalator is h, the work done by the man in going up the escalator is

A

zero

B

`mgh`

C

`(mgh upsilon)/((upsilon - u))`

D

`(mghv)/((upsilon - u))`

Text Solution

Verified by Experts

The correct Answer is:
D
Relative speed of man with respect to escalator = `( upsilon - u)`
`therefore` Actual displacement of man per second `=( upsilon -u)`
Hence, the actual displacement of man in going up the escalator of height h is `(upsilon h)/((upsilon - u))` . Therefore, Work done = `mg xx (upsilon h)/((upsilon - u))` which is choice (D)
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