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Gravitation question

2025 · 2 Apr · Shift 2 · Q75
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Gravitation question

2025 · 2 Apr · Shift 2 · Q75

JEE MainPhysicsGravitationNumerical+4 / −1
A satellite of mass 1000 kg is launched to revolve around the earth in an orbit at a height of 270 km from the earth's surface. Kinetic energy of the satellite in this orbit is ‾×1010 J\underline{\hspace{2cm}}\times 10^{10} \mathrm{~J}​×1010 J. (Mass of earth =6×1024 kg=6 \times 10^{24} \mathrm{~kg}=6×1024 kg, Radius of earth =6.4×106 m=6.4 \times 10^6 \mathrm{~m}=6.4×106 m, Gravitational constant =6.67×10−11Nm2 kg−2=6.67 \times 10^{-11} \mathrm{Nm}^2 \mathrm{~kg}^{-2}=6.67×10−11Nm2 kg−2 )
Numerical answer
View written solutionFree

Correct answer: 3

  1. Given data
  • Mass of satellite: m=1000 kgm = 1000\,\text{kg}m=1000kg
  • Mass of earth: M=6×1024 kgM = 6 \times 10^{24}\,\text{kg}M=6×1024kg
  • Radius of earth: R=6.4×106 mR = 6.4 \times 10^6\,\text{m}R=6.4×106m
  • Height above earth: h=270 km=2.7×105 mh = 270\,\text{km} = 2.7 \times 10^5\,\text{m}h=270km=2.7×105m
  • Gravitational constant: G=6.67×10−11 N m2kg−2G = 6.67 \times 10^{-11}\,\text{N m}^2\text{kg}^{-2}G=6.67×10−11N m2kg−2
  1. Orbital radius

For the satellite, r=R+h=6.4×106+2.7×105=6.67×106 mr = R + h = 6.4 \times 10^6 + 2.7 \times 10^5 = 6.67 \times 10^6\,\text{m}r=R+h=6.4×106+2.7×105=6.67×106m

  1. Kinetic energy in circular orbit

For a satellite in circular orbit, K=GMm2rK = \frac{GMm}{2r}K=2rGMm​

  1. Substitute values

K=(6.67×10−11)(6×1024)(1000)2(6.67×106)K = \frac{(6.67 \times 10^{-11})(6 \times 10^{24})(1000)}{2(6.67 \times 10^6)}K=2(6.67×106)(6.67×10−11)(6×1024)(1000)​

First simplify numerator: 6.67×6×10−11+24+3=40.02×10166.67 \times 6 \times 10^{-11+24+3} = 40.02 \times 10^{16}6.67×6×10−11+24+3=40.02×1016

Denominator: 2×6.67×106=13.34×1062 \times 6.67 \times 10^6 = 13.34 \times 10^62×6.67×106=13.34×106

So, K=40.02×101613.34×106K = \frac{40.02 \times 10^{16}}{13.34 \times 10^6}K=13.34×10640.02×1016​

K=3.0×1010 JK = 3.0 \times 10^{10}\,\text{J}K=3.0×1010J

  1. Required integer

The kinetic energy is 3×1010 J3 \times 10^{10}\,\text{J}3×1010J

So the blank is 333.

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