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Gravitation question

2020 · Q121
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Gravitation question

2020 · Q121

NEETPhysicsGravitationMCQ+4 / −1
A body weighs 72 N on the surface of the earth. What is the gravitational force on it, at a height equal to half the radius of the earth?
  1. A
    32 N
  2. B
    30 N
  3. C
    24 N
  4. D
    48 N
View written solutionFree

Correct answer: A

We know W = mg

At a height h, above the surface of earth, weight is given as,

mgh=mg[(1+hR)2]mgh = {{mg} \over {\left[ {{{\left( {1 + {h \over R}} \right)}^2}} \right]}}mgh=[(1+Rh​)2]mg​

=72(1+R/2R)2 = {{72} \over {{{\left( {1 + {{R/2} \over R}} \right)}^2}}}=(1+RR/2​)272​

=72(32)2 = {{72} \over {{{\left( {{3 \over 2}} \right)}^2}}}=(23​)272​

=49×72=32N = {4 \over 9} \times 72 = 32N=94​×72=32N

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