Physics

Gravitation and Orbital Mechanics

522 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

The spinning of an object around a center point

  1. Rotation

  2. Axis

  3. Solar System

  4. Revolution
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rotation is the action of spinning around an internal axis. This is different from revolution, which is the movement around an external point.

Multiple choice physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

What is the time period satellite near the earth surface (neglect the height of orbit of satellite from the surface of ground)?

  1. $30.53 \ minutes$
  2. $50.38 \ minutes$
  3. $52.68 \ minutes$
  4. $84.75 \ minutes$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$T =$ Time period

$R=$ radius of earth $= 6400000m$
Gravitational constant $= G=$ $ 6.67\times {10}^{-11} Nm^2/kg^2$
$M=$ mass of earth $=$ $6\times{10}^{24}kg$

$T=$ $2\pi\sqrt{\dfrac {R^3}{GM}}$
Substitute and calculate
Whatever answer you get, divide it by $60$ so that it gets converted into minutes.

Multiple choice stefan's law black body radiation heat transfer thermal properties physics

A planet is at an average distance $d$ from the sun and its average surface temperature is $T$. Assume that the planet receives energy only from the sun and loses energy only through radiation from the surface. Neglect atmospheric effects. If $T$ $\propto d^{-n}$, the value of $n$ is :

  1. $2$
  2. $1$
  3. $\displaystyle \frac{1}{2}$
  4. $\displaystyle \frac{1}{4}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let P=power radiated by Sun
R=Radius of planet
E=energy received by planet=$\cfrac{P}{4 \pi d^2}\times \pi R^2$
Energy radiated by planet=$(4 \pi R^2)\sigma T^4 $
For thermal equilibriums:
$\Rightarrow \cfrac { P }{ 4\pi d^{ 2 } } \pi R^{ 2 }=4\pi R^{ 2 }\sigma T^{ 4 }\\ \Rightarrow T^{ 4 }\alpha \cfrac { 1 }{ d^{ 2 } } \\ \Rightarrow T\alpha \cfrac { 1 }{ d^{ { 1 }/{ 2 } } } \\ \Rightarrow T\alpha { d }^{ -\cfrac { 1 }{ 2 }  }$
So n=$\cfrac{1}{2}$
Multiple choice stefan's law black body radiation heat transfer thermal properties physics

Solar constant for earth is $2 \mathrm { cal } / \mathrm { min } \mathrm { cm } ^ { 2 } ,$ if distance ofmerary from sun is 0.4 times than distance of earthfrom sun then solar constant for mercury will be? 

  1. 12.5$\mathrm { cal } / \mathrm { min } \mathrm { cm } ^ { 2 }$
  2. 25$\mathrm { cal } / \mathrm { min } \mathrm { cm } ^ { 2 }$
  3. 0.32$\mathrm { cal } / \mathrm { min } \mathrm { cm } ^ { 2 }$
  4. 2$\mathrm { cal } / \mathrm { min } \mathrm { cm } ^ { 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice stefan's law black body radiation heat transfer thermal properties physics

The temperature of a spherical planet is related to the distance from sun as :

  1. $T \propto 1/d^{2}$
  2. $T\propto \dfrac{1}{\sqrt{d}}$
  3. $T\propto d$
  4. $T\propto d^{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
A planet reaches its equilibrium temperature when the amount of heat it absorbs from the sun is equal to the amount that it radiates back to space.
The energy absorbed is equal to the insolation at planet's distance (which is Sun's bolometric output divided by $4\pi$ times the distance squared) times the planet's profile area times the planet's Bond aldedo. The amount radiated (assuming that the thermal radiation is approximately black body radiation) is proportional to the planet's surface area times its emmisivity times the forth power of its temperature.

Now, throwing away 2, $\pi$ and other constants that do not vary with temperature or distance.
${ T }^{ 4 }\alpha \cfrac { 1 }{ { d }^{ 2 } } \\ \Rightarrow T\alpha \cfrac { 1 }{ \sqrt { d }  } $
Multiple choice

What is the approximate orbital period of Halley's Comet?

  1. 76 years

  2. 100 years

  3. 150 years

  4. 200 years
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Halley's Comet has an orbital period of approximately 76 years, meaning it takes about 76 years to complete one orbit around the Sun.

Multiple choice

Which of Kepler's laws states that the planets move in elliptical orbits with the Sun at one focus?

  1. First Law

  2. Second Law

  3. Third Law

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Kepler's First Law, also known as the Law of Ellipses, states that the planets move in elliptical orbits with the Sun at one focus.

Multiple choice

According to Kepler's Second Law, a line connecting a planet to the Sun sweeps out equal areas in equal times.

  1. True

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

Kepler's Second Law, also known as the Law of Equal Areas, states that a line connecting a planet to the Sun sweeps out equal areas in equal times.

Multiple choice

The square of the orbital period of a planet is proportional to the cube of its average distance from the Sun.

  1. True

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

Kepler's Third Law, also known as the Law of Periods, states that the square of the orbital period of a planet is proportional to the cube of its average distance from the Sun.

Multiple choice

Which of the following is not a consequence of Kepler's Laws?

  1. Planets move in circular orbits.

  2. The Sun is at the center of the solar system.

  3. The planets' orbits are elliptical.

  4. The planets' orbital periods are proportional to their distances from the Sun.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Kepler's Laws state that the planets move in elliptical orbits, not circular orbits.

Multiple choice

The semi-major axis of an elliptical orbit is the average distance of the planet from the Sun.

  1. True

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

The semi-major axis of an elliptical orbit is the average distance of the planet from the Sun.

Multiple choice

Kepler's Laws apply to all objects orbiting the Sun, including planets, moons, asteroids, and comets.

  1. True

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

Kepler's Laws apply to all objects orbiting the Sun, regardless of their size or composition.

Multiple choice

The perihelion of an elliptical orbit is the point where the planet is closest to the Sun.

  1. True

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

The perihelion of an elliptical orbit is the point where the planet is closest to the Sun.

Multiple choice

The aphelion of an elliptical orbit is the point where the planet is farthest from the Sun.

  1. True

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

The aphelion of an elliptical orbit is the point where the planet is farthest from the Sun.