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To a man running upwards on the hill, th...

To a man running upwards on the hill, the rain appears to fall vertically downwards with `4 m s^-1`. The velocity vector of the man w.r.t. earth is `(2 hat i + 3 hat j) ms ^-1`. If the man starts running down the hill with the same speed, then determine the relative speed of the rain w.r.t. man.
.

A

`sqrt(10) ms^(-1)`

B

`sqrt(20) ms^(-1)`

C

`sqrt(30) ms^(-1)`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
b

Velocity of man relative to earth `overset(rarr)V_(m)//E =2 hat I + 3 hatj`
velocity of rain relative to man `overset(rarr)v_(R)//M=-4hat j`
`=2hat i-hatj -2hati-3hati=4 hat I +2 hat j |overset(rarr)v_(R //M)|=sqrt(4^(2)+2^(2))=sqrt(20) ms^(-1)`
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