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

When a man circles around the earth in a satellite, _____.

  1. his weight remains constant but mass becomes zero

  2. his mass remains constant but weight becomes zero

  3. both his mass and weight remain constant

  4. both his mass and weight become zero
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mass is an intrinsic property of matter that remains constant everywhere. Weight = mass × gravitational acceleration. In a satellite orbiting Earth, the astronaut and satellite are in free-fall, experiencing apparent weightlessness despite gravity still acting - this is why objects float inside spacecraft.

Multiple choice

A geostationary satellite has a time period _______ the rotational period of the earth.

  1. double than

  2. same as

  3. thrice than

  4. four times than
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A geostationary satellite appears stationary from Earth's surface because its orbital period exactly matches Earth's rotational period (approximately 24 hours). This requires the satellite to be at a specific altitude (~35,786 km above equator) where its orbital period equals one sidereal day.

Multiple choice

The period of revolution of a geostationary satellite is

  1. 24 hours

  2. 30 hours

  3. 365 days

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

A geostationary satellite must complete one orbit in the same time Earth takes to rotate once - approximately 24 hours (23 hours, 56 minutes, 4 seconds precisely). This allows it to remain fixed relative to a point on Earth's surface.

Multiple choice

Directions: Read the passage and answer the question.

A comet is an icy small solar system body made up of ices mixed with smaller amounts of dust and rock. It is no larger than few kilometers across. The main structure of a comet is know as nucleus. Comets are composed primarily of many varieties of ice including water, methane and other gases. Comets usually orbit the sun. While planets have a circular orbit, comets' orbits are usually very elliptical. As a comet moves closer to the Sun, the ices begin to fizz. The closest point in its orbit to the Sun is known as “perihelion” and the farthest one is known as “aphelion”. Comets are not any kind of spaceship or alien base. They are bits of solar system material.

_________ is the most distant point to a comet's orbit to the Sun.

  1. Perihelion

  2. Elliptical

  3. Aphelion
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The farthest one is known as “aphelion”.

Multiple choice

Directions: The following question contains paragraph with sentence or phrase missing indicated parenthetically. From the alternatives, select the sentence or phrase that best provides the missing link. As an unseen planet orbits a distant star, the gravitational pull causes the star to move back and forth in space. ( _____ ). The AAT team measures the Doppler shift of stars to an accuracy of 3 metres per second –bicycling speed. This very high precision allows the team to find planets.

  1. At planetary spectacle can be detected by ‘Doppler shifting’

  2. ‘Doppler shifting’ can detect this pull in the bicycling speed.

  3. This causes a shift in the absolute location of the star itself.

  4. That wobble can be detected by the ‘Doppler shifting’ it causes in the star’s light.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

(4) The clue is in the purpose. “This very high precision allows the team to find planets”. The accuracy is important.

Multiple choice

Why do planets revolve around the sun in definite elliptical orbits?

  1. Friction between the sun and the planets makes the planets revolve.

  2. The planets exert gravitational pull among each other.

  3. The planets are spherical in shape.

  4. There is a magnetic pull between the planets and the sun.

  5. The sun exerts immense gravitational pull.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The sun exerts immense gravitational pull due to which the planets revolve around it in an elliptical orbit.

Multiple choice

Consider the following statements:

  1. The speed of the body continuously changes in uniform circular motion.
  2. Earth moves around the sun with a uniform velocity.

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1 is incorrect. In circular motion, the speed of the body always remains the same. Statement 2 is incorrect. The earth's orbit around the sun is elliptical. So, the earth moves at a constantly varying velocity as it moves closer to the sun.

Multiple choice

The earth revolves around the sun, the center of solar system, at about 30 m/s. Is the earth in accelerated motion?

  1. No, as acceleration is a vector.

  2. No, as the net displacement is zero.

  3. Yes, as the speed is not constant.

  4. Yes, as the velocity is not constant.

  5. The data is insufficient.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Acceleration is defined as the rate of change of velocity. Both acceleration and velocity are vector quantities. As the direction of the earth's motion is constantly changing, so is velocity changing and thus earth is in accelerated motion.

Multiple choice

Each planet tends to be roughly twice as far from the sun as its next Sunward neighbour. This is called

  1. Bode's Law

  2. Hawkin's Law

  3. Bagnold's Law

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

Each planet tends to be roughly twice as far from the sun as its next Sunward neighbour. This is called Bode's Law. The Titius-Bode law is a hypothesis that the bodies in some orbital systems, including the Sun's orbit at semi-major axes in a function of planetary sequence. The hypothesis correctly predicted the orbits of Ceres and Uranus, but failed as a predictor of Neptune's orbit.

Multiple choice

Planets do not collide while revolving around the sun because

  1. period of revolution increases as the distance of planet increases

  2. planets move in their own orbit

  3. all planets maintain distance from each other while revolving

  4. planets also rotate on their own axis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Option (2) is the correct answer.