Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Gravitation question

2023 · 8 Apr · Shift 1 · Q51
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Gravitation
  5. /2023 · 8 Apr · Shift 1 · Q51

Gravitation question

2023 · 8 Apr · Shift 1 · Q51

JEE MainPhysicsGravitationMCQ+4 / −1
Given below are two statements: Statement I: If E\mathrm{E}E be the total energy of a satellite moving around the earth, then its potential energy will be E2\frac{E}{2}2E​. Statement II: The kinetic energy of a satellite revolving in an orbit is equal to the half the magnitude of total energy E\mathrm{E}E. In the light of the above statements, choose the most appropriate answer from the options given below
  1. A
    Both Statement I and Statement II are incorrect
  2. B
    Statement I is incorrect but Statement II is correct
  3. C
    Statement I is correct but Statement II is incorrect
  4. D
    Both Statement I and Statement II are correct
View written solutionFree

Correct answer: A

  1. Recall the energy relations for a satellite in a bound circular orbit

For a satellite of mass mmm orbiting Earth of mass MMM at radius rrr:

  • Gravitational potential energy: U=−GMmrU=-\frac{GMm}{r}U=−rGMm​
  • Orbital speed from gravitational force providing centripetal force: mv2r=GMmr2  ⟹  v2=GMr\frac{mv^2}{r}=\frac{GMm}{r^2}\implies v^2=\frac{GM}{r}rmv2​=r2GMm​⟹v2=rGM​
  • Hence kinetic energy: K=12mv2=12m⋅GMr=GMm2rK=\frac{1}{2}mv^2=\frac{1}{2}m\cdot \frac{GM}{r}=\frac{GMm}{2r}K=21​mv2=21​m⋅rGM​=2rGMm​
  1. Find total energy

E=K+U=GMm2r−GMmr=−GMm2rE=K+U=\frac{GMm}{2r}-\frac{GMm}{r}=-\frac{GMm}{2r}E=K+U=2rGMm​−rGMm​=−2rGMm​

So for a satellite in orbit: K=−EK=-EK=−E and U=2EU=2EU=2E

since 2E=2(−GMm2r)=−GMmr=U2E=2\left(-\frac{GMm}{2r}\right)=-\frac{GMm}{r}=U2E=2(−2rGMm​)=−rGMm​=U

  1. Check Statement I

Statement I says: potential energy is E2\frac{E}{2}2E​.

But actually, U=2EU=2EU=2E not U=E2U=\frac{E}{2}U=2E​

So Statement I is incorrect.

  1. Check Statement II

Statement II says: kinetic energy is equal to half the magnitude of total energy EEE.

Now, ∣E∣=GMm2r|E|=\frac{GMm}{2r}∣E∣=2rGMm​ And K=GMm2r=∣E∣K=\frac{GMm}{2r}=|E|K=2rGMm​=∣E∣

Thus kinetic energy is equal to the full magnitude of total energy, not half of it.

So Statement II is also incorrect.

  1. Choose the correct option

Therefore, both Statement I and Statement II are incorrect.

So the correct option is: A\boxed{A}A​

  1. Comparison with stored answer

Stored correct answer: AAA

My derived answer also is AAA, so they agree.

PreviousNext

More from Gravitation

  • The weight of a body on the earth is 400 N. Then weight of the body when taken to a depth half of the radius of the earth will be:2023 · MCQ
  • The acceleration due to gravity at height h above the earth if h<<R (Radius of earth) is given by2023 · MCQ
  • The orbital angular momentum of a satellite is L, when it is revolving in a circular orbit at height h from earth surface. If the distance of satellite from the earth centre is increased by eight times to its initial value, then the new…2023 · MCQ
  • Two satellites of masses m and 3m revolve around the earth in circular orbits of radii r & 3r respectively. The ratio of orbital speeds of the satellites respectively is2023 · MCQ
  • Assuming the earth to be a sphere of uniform mass density, the weight of a body at a depth d=2R​ from the surface of earth, if its weight on the surface of earth is 200 N, will be: (Given R = radius of earth)2023 · MCQ
  • If the earth suddenly shrinks to 641​ th of its original volume with its mass remaining the same, the period of rotation of earth becomes x24​ h. The value of x is ​.2023 · Numerical
  • The time period of a satellite, revolving above earth's surface at a height equal to R will be (Given g=π2 m/s2,R= radius of earth)2023 · MCQ
  • Given below are two statements: Statement I : Rotation of the earth shows effect on the value of acceleration due to gravity (g) Statement II : The effect of rotation of the earth on the value of 'g' at the equator is minimum and that at…2023 · MCQ