1.

A ping-pong ball of mass `m` is floating in air by a jet of water emerging out of a nozzle. If the water strikes the ping-gong ball with a speed `v` and just after collision water falls dead, the rate of flow of water in the nozzle is equal toA. `(2mg)/V`B. `(mV)/g`C. `(mg)/V`D. none of these

Answer» Correct Answer - C
The impact force `F=(/_p)/(/_ )` where `/_p=` change of momentum of water of mass `/_m` striking the pendulum with a speed `v` during the `/_ `. Since water falls dead after collision with the ping pong ball.
`/_p=/_mvimpliesF=v(/_m)/(/_ )`
where `(/_m)/(/_ )=` rate of flow of wate in the nozzle.
Since the ball is in equlibrium
`F-mg=0impliesF=mg`
` implies(v/_m)/(/_ )=mgimplies(/_m)/(/_ )=(mg)/v`


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