1.

A particle is projected with a velocity `u` making an angle `theta` with the horizontal. The instantaneous power of the gravitational forceA. (a) Varies linearly with timeB. (b) Is constant throughoutC. (c) Is negative for complete pathD. (d) None of the above

Answer» Correct Answer - A
At any time,
`vecv=[u cos theta]hati+(u cos theta-g t)hatj`
`P=vecF.vecv=(-mghatj)*[u cos thetahatj+(u sin theta-g t)hatj]`
`=mg^2t-mgu sin theta`
Hence, power varies linearly with time.


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