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JEE Main 2022 · 26 Jul · Shift 2, Physics question 38

A body is projected vertically upwards from the surface of earth with a velocity equal to one third of escape velocity. The maximum height attained by the body will be :

(Take radius of earth = 6400 km and g = 10 ms−2^{-2})

Choose one option
Answer and worked solution

Official answer: A

Energy. With v2=ve29=2gR9v^2=\frac{v_e^2}9=\frac{2gR}9: 12v2=gR−gR2R+h\frac12v^2=gR-\frac{gR^2}{R+h} gives RR+h=89\frac R{R+h}=\frac89.

h=R8=800h=\frac R8=800 km. (A)

Topics:Escape velocityGravitational field and potential
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