Physics

Gravitation and Orbital Mechanics

500 Questions

Gravitation and orbital mechanics focus on planetary motion, elliptical orbits, and satellite deployment. Questions examine astrodynamics fundamentals, including geostationary orbits and perturbation theory. These topics are highly relevant for civil services and specialized technical examinations.

Planetary orbitsSatellite dynamicsGeostationary orbitsPerturbation theoryOrbital eccentricity

Gravitation and Orbital Mechanics Questions

Multiple choice physics universe and space science launching of an artificial satellites around the earth launching of satellite india’s space programmes

Geo stationary satelites revolves at:

  1. Any height

  2. Fixed height

  3. Height above pole

  4. height which depends upon its mass
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Geo stationary satellite revolves at fixed height. A Geo stationary satellite is an earth orbiting satellite which is placed at an altitude of approximately 35,800 kms directly over the equator, that revolves in the same direction the earth rotates.

Multiple choice physics search of life outside earth space research and satellites artificial satellites space missions and artificial satellites

A satellite of mass $m$ revolving around the earth in a circular orbit of radius $2R$ has to be shifted to another circular orbit of radius $4R$. The energy required for this process will be ($M\rightarrow$ mass of earth, $R\rightarrow$ radius of the earth)

  1. $\dfrac {GMm}{8R}$
  2. $\dfrac {2GMm}{3R}$
  3. $\dfrac {GMm}{4R}$
  4. $\dfrac {GMm}{6R}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The total energy of a satellite in an orbit of radius r is E = -GMm / (2r). The energy required to move from 2R to 4R is E2 - E1 = (-GMm / 8R) - (-GMm / 4R) = (-GMm + 2GMm) / 8R = GMm / 8R.

Multiple choice evs search of life outside earth space research and satellites artificial satellites space missions and artificial satellites

Remote imaging satellites are placed in geostationary orbit. This statement is

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.
Geostationary satellites are positioned at an height above the Earth about $36,000\ km$. At this height, they rotate around the Earth at the same speed as the Earth rotates around its axis, so in effect remaining stationary above a point on the Earth (normally directly overhead the equator).
As they remain stationary, they are ideal for use as communications satellites and also for remote imaging as they can repeatedly scan the same points on the Earth beneath them.
Their great height is that they can view the whole Earth disk below them, rather than a small subsection, and they can scan the same area very frequently.
Hence, the statement is true.

Multiple choice physics circular motion and gravitation elementary ideas of astronomy shadow formation and optical medium light and shadow

A satellite of mass $m$ is revolving around the earth at height $R$ (radius of the earth) from the earth's surface. Its potential energy will be :

  1. $mgR$
  2. $0.67 mgR$
  3. $-\dfrac{mgR}{2}$
  4. $0.33mgR$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The gravitational potential energy of a satellite of mass m at a distance r from the center of the earth is given by U = -G M m / r. Here, the height is R from the surface, so the distance from the center is r = R + R = 2R. Substituting M = g R^2 / G gives U = -mgR / 2.

Multiple choice physics gravitation elementary ideas of astronomy shadow formation and optical medium light and shadow

Suppose an earth satellite, revolving in a circular orbit experiences a resistance due to cosmic dust. Then.

  1. Its kinetic energy will increase

  2. Its potential energy will decrease

  3. It will spiral towards the earth and in the process its angular momentum will remain conserved

  4. Both a and b is correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The Kinetic energy of the satellite increases in spiral path as it approach the earth so $V$ must increase the total mechanical energy of the satellite decreases due to resistance from conic dust as satellite approaches earth so potential energy decreases.
Thus Kinetic energy increase potential energy decreases.
Multiple choice physics space missions launching of an artificial satellites around the earth launching of satellite india’s space programmes

ENERGY OF AN ORBITING SATELLITE
In motion of an object under the gravitational influence of another object. Which of the following quantities is not conserved?

  1. Angular momentum

  2. mass of an object

  3. Total mechanical energy

  4. Linear momentum
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

While considering the motion of an object under the gravitational influence of another object, angular momentum and total mechanical energy are conserved.Linear momentum is not conserved

Multiple choice physics space missions launching of an artificial satellites around the earth launching of satellite india’s space programmes

The minimum distance of a satellite from the centre of the earth is 3R, where R is the radius of 2GM What is the earth. The mass of earth is M. The maximum speed of the satellite is $\sqrt { \frac { 2 G M } { 3 R } }$ radius of curvature at the point of minimum distance?

  1. 6 R

  2. 4 R

  3. 3 R
  4. $\frac { 9 R } { 2 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} F=\dfrac { { G\left( M \right) m } }{ { { { \left( { 3R } \right)  }^{ 2 } } } }  \ \Rightarrow a=\dfrac { { GM } }{ { 9{ R^{ 2 } } } }  \ \therefore \dfrac { { { V^{ 2 } } } }{ { R' } } =a \ \Rightarrow \dfrac { { 2GM } }{ { 3R.R' } } =\dfrac { { GM } }{ { 9{ R^{ 2 } } } }  \ \Rightarrow R'=6R \ Hence, \ option\, \, A\, \, is\, \, correct\, \, answer. \end{array}$

Multiple choice lorentz transformation and muon experiment option a: relativity physics

Suppose a new planet is discovered, which revolves around the sun (i.e. it is a part of our solar system). If its lies between saturn and Jupitar, its time period of revolution would be 

  1. Less than that of Jupiter

  2. More than that of Jupiter

  3. Equal to that of Jupiter or saturn

  4. More than that of saturn.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We don't know the exact order of all the planets, but Jupiter formed first, with Saturn close behind. Both were finished in less than 3 million years. The inner planets (Mercury, Venus, Earth, Mars) got off to a late start.

Multiple choice physics artificial satellite communication and mass media understanding communication and impact of mass media satellites in communication

As the height of a satellite orbit gets lower, the speed of the satellite _________.

  1. decreases

  2. increases

  3. remains the same

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$V=\sqrt { \cfrac { GMe }{ r }  } \ \therefore V\propto \cfrac { 1 }{ \sqrt { r }  } $

With decrease in $'r'$, velocity of satellite $increases$.

Multiple choice physics artificial satellite communication and mass media understanding communication and impact of mass media satellites in communication

Let $R _s$ and $R _m$ be the distance of the geostationary satellite and moon from the center of earth. Then $\dfrac{R _m}{R _s}$ is

  1. $(29)^{1/2}$
  2. $(29)^{2/3}$
  3. $29$
  4. $(29)^{3/2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using Kepler's Third Law, T^2 is proportional to R^3. For a geostationary satellite, T is 1 day. For the moon, T is approximately 29 days. Thus, (Rm/Rs)^3 = (Tm/Ts)^2 = (29/1)^2, which means Rm/Rs = (29^2)^(1/3) = 29^(2/3).

Multiple choice physics artificial satellite communication and mass media understanding communication and impact of mass media satellites in communication

A remote -sensing satellite of earth revolves in a circular orbit at a height of $ 0.25 \times 10^6 $ m above the surface of earth. if earth's radius is $ 0.25 \times 10^6 $ m above the surface of earth. if earth's radius is $ 6.38 \times 10^6 m $ and $ g= 9.8 m/s^2 $, then the orbital speed of the satellite is :

  1. $6.67 km/s$
  2. $7.76 km/s$
  3. $8.56 km/s$
  4. $9.13 km/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

For a rigit body, we know that if verious forces act at various points in it , the resultant motion is as if a net force acts on the CM(centre of mass)  causing translation and a net torque at the CM causing rotation around an axis through the CM. for the earth-sun system (approximating the earth as a uniform density sphere).

  1. the torque is zero

  2. the torque causes the earth to spin

  3. the rigid body result is not applicable since the earth is not ever approximately a rigid body

  4. the torque causes the earth to move around the sun
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the Earth-Sun system, the gravitational force acts on the Earth, and because the Earth is not a point mass but an extended body, the gravitational gradient creates a torque that contributes to the Earth's axial precession and spin dynamics.

Multiple choice physics turning on a pivot the turning effect of a force moment of force or torque turning effect of force couple

A small piece of space junk is at rest in outer space. A very small asteroid strikes it, exerting a force on it that is NOT directed through the piece of space junk's center of mass.
Which of the following describes the motion of the piece of space junk DURING the asteroid strike?

  1. Because the asteroid is small, the space junk remains at rest

  2. The piece of space junk spins, but does NOT move linearly

  3. The piece of space junk moves at constant velocity linearly, but does NOT spin

  4. The piece of space junk accelerates linearly, but does NOT spin

  5. The piece of space junk accelerates linearly, AND spins
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Due to striking the space junk, the asteroid will exert a force on the junk piece.

This force is not directed towards the of mass of the junk.
Hence the junk would experience a linear acceleration given by $a=\dfrac{F}{m}$
And also the angular acceleration as provided by the force=$\dfrac{Fl}{I}$
where $l$ is the least distance between the center of mass of junk and line along which asteroid moves,
and $I $ is the moment of inertia of the space junk.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The critical velocity of satellite of mass $100 kg$ moving round a planet is $20 m/s$. If another satellite of mass $200 kg$ is kept moving in the same orbit then its critical velocity will be:

  1. $40 km/hr$
  2. $72 km/hr$
  3. $40 m/s$
  4. $72 m/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The critical velocity (orbital velocity) of a satellite is given by v = sqrt(GM/r). It is independent of the mass of the satellite. Therefore, the velocity remains 20 m/s. Converting 20 m/s to km/hr: 20 * (3600/1000) = 72 km/hr.