1.

The earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of earth. The escape velocity of a body from this platform is fv, where v is its escape velocityfrom surfaceof the earth. The value of f is :

Answer»

`(1)/(2)`
`sqrt(2)`
`(1)/(sqrt(2))`
`(1)/(3)`.

Solution :Escape velocity from surface of earth is
`v=sqrt((2GM)/(R ))`
If v. is escape velocity from the platform then Kinetic energy + Gravitational POTENTIAL energy = 0.
`(1)/(2)mv.^(2)+(-(GMm)/(2R))=0 rArr v.= sqrt((GM)/(R ))=FV`
`THEREFORE f=(v.)/(v)=(1)/(sqrt(2))`.
Thus correct choice is (c ).


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