1.

A satellite of mass m is revolving round the earth at a height R above surface of earth. If g is gravitational intensity at earth's surface and R is radius of the earth, the K.E. of satellite is :

Answer»

`"mg" (R )/(4)`
`"mg"(R )/(2)`
`"mg" R`
`"2mg" R`

SOLUTION :Here gravitational force provides CENTRIPETAL force
`therefore (mv^(2))/(2R)=(GMM)/((2R)^(2)) rArr (1)/(2)mv^(2)=(GMm)/(4R)=(mgR)/(4)`
or `K.E.=-(1)/(2) (GP.E.)= -(1)/(2)`
`((-GMm)/(2R))=(GMm)/(4R)=(mgR)/(4)`
Thus CORRECT choice is (a).


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