1.

The kinetic energy needed to project a body of mass `m` from the earth surface (radius R) to infinity isA. `(mgR)/(2)`B. `2mgR`C. `mgR`D. `(mgR)/(2)`

Answer» Correct Answer - C
The kinetic energy needed to project a body of mass m from the earth surface to infinity is given by
`KE=(1)/(2)mv_(e)^(2)=(1)/(2)m 2Rg`
`(because "Escape velociy", v_(e)=sqrt(2Rg)rArrv_(e)^(2)=2Rg)`
`rArr KE = mRg`


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