    Question

# The total mechanical energy of an object of mass m projected from surface of earth with escape speed is

A
Zero
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B
Infinite
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C
GMm2R
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D
GMm3R
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Solution

## The correct option is A ZeroGiven, Mass of the object=m If M is the mass and R is the radius of the earth, then the escape velocity from its surface is given by,ve=√2GMRTotal mechanical energy (M.E) = K.E + P.E ⇒M.E = 12mv2e−GMmR Substituting the values of ve, ⇒M.E=12m×2GMR−GMmR ⇒M.E =0 Hence, option (a) is the correct answer. Key Concept: The escape velocity for a planet is given by, ve=√2GMRWhy this question: To note that the potential energy when the masses are far apart is assumed to be zero.  Suggest Corrections  0      Similar questions  Explore more