Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 20199 JanuaryEvening Shift
Exam
JEE Main
Year
2019
Date
9 January
Shift
Evening Shift
Subject
Physics
Chapter
Gravitation

JEE Main 2019 · 9 January · Evening Shift · Physics · Gravitation

The energy required to take a satellite to a height h above the...

The energy required to take a satellite to a height $hhabove the Earth surface (radius of Earth =6.4×103km= 6.4 \times {10}^{3}km ) is E1{E}_{1}, and the kinetic energy required for the satellite to be in a circular orbit at this height is E2.{E}_{2} . The value of hh for which E1{E}_{1} and E2{E}_{2} are equal, is$

Options

  1. A1.28×104km1.28 \times {10}^{4}km
  2. B6.4×103km6.4 \times {10}^{3}km
  3. C3.2×103km3.2 \times {10}^{3}km
  4. D1.6×103km1.6 \times {10}^{3}km

Correct answer

C. 3.2×103km3.2 \times {10}^{3}km

Step-by-step solution

Usurface+E1=Uh{U}_{surface} + {E}_{1} = {U}_{h}

KEKE of satellite is zero at earth surface and at height hh

−GMemRe+E1=−GMem(Re+h)- \dfrac{G{M}_{e}m}{{R}_{e}} + {E}_{1} = - \dfrac{G{M}_{e}m}{\left({R}_{e} + h\right)}

E1=GMem(1Re−1Re+h){E}_{1} = G{M}_{e}m\left(\dfrac{1}{{R}_{e}} - \dfrac{1}{{R}_{e} + h}\right)

E1=GMem(Re+h)×hRe{E}_{1} = \dfrac{G{M}_{e}m}{\left({R}_{e} + h\right)} \times \dfrac{h}{{R}_{e}}

Gravitational attraction FG=maC=mv2(Re+h){F}_{G} = m{a}_{C} = \dfrac{m{v}^{2}}{\left({R}_{e} + h\right)}

⇒mv2(Re+h)=GMem(Re+h)2⇒ \dfrac{m{v}^{2}}{\left({R}_{e} + h\right)} = \dfrac{G{M}_{e}m}{{\left({R}_{e} + h\right)}^{2}}

mv2=GMem(Re+h)m{v}^{2} = \dfrac{G{M}_{e}m}{\left({R}_{e} + h\right)}

E2=mv22=GMem2(Re+h){E}_{2} = \dfrac{m{v}^{2}}{2} = \dfrac{G{M}_{e}m}{2\left({R}_{e} + h\right)}

E1=E2{E}_{1} = {E}_{2}

hRe=12⇒h=Re2=3200km\dfrac{h}{{R}_{e}} = \dfrac{1}{2} ⇒ h = \dfrac{{R}_{e}}{2} = 3200km

Practice Gravitation on Quantrex Academy →

More from Gravitation

A particle of mass m , and angular momentum ℓ is moving in a circular orbit of radius r_0… JEE Advanced 2026A body of mass m is taken from the surface of earth to a height equal to twice the radius… JEE Main 2026When one moves from a point 16 km below the earth's surface to a point 16 km above the… JEE Main 2026The height in terms of radius of the earth (R) , at which the acceleration due to gravity… JEE Main 2026If a body of mass 1 kg falls on the earth from infinity, it attains velocity (v) and… JEE Main 2026A planet (P_1) is moving around the star of mass 2M in the orbit of radius R . Another… JEE Main 2026Three masses 200 ~kg, 300 ~kg and 400 kg are placed at the vertices of an equilateral… JEE Main 2026Given below are two statements: Statement I : A satellite is moving around earth in the… JEE Main 2026 Full Gravitation list All JEE Main PYQs