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The orbital velocity of an artificial satellite in a circular orbit just above the earth's surface is v . For a satellite orbiting at an altitude of half of the earth's radius, the orbital velocity is

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Important Questions on Gravitation

EASY
A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth. Then,
EASY
A planet is moving in a circular orbit. It completes 2 revolutions in 360 days. What is its angular frequency?
MEDIUM
Two satellites A and B are revolving with critical velocities vA and vB around the earth, in circular orbits of radii R and 2R respectively. The ratio vAvB is
HARD
Two satellites A and B of masses 200 kg and 400 kg are revolving round the earth at height of 600 km and 1600 km respectively. If TA and TB are the time periods of A and B respectively then the value of TB-TA :

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[ Given : radius of earth =6400 km, mass of earth =6×1024 kg ]

EASY
An astronaut of mass m is working on a satellite orbiting the earth at a distance h from the earth's surface. The radius of the earth is R, while its mass is M. The gravitational pull FG on the astronaut is
MEDIUM

Which of the following is not true about the total lunar eclipse?

 

EASY
A satellite is launched to a distance r from the centre of the earth to have a circular orbit around the earth. Its orbital velocity to maintain this orbit is (mass of the earth as ME)
MEDIUM
A geostationary satellite is taken to a new orbit such that its distance from centre of the earth is doubled. Then find the time period of this satellite in the new orbit.
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A test particle is moving in a circular orbit in the gravitational field produced by a mass density ρr=Kr2. Identify the current relation between the radius R of the particle’s orbit and its period T:
MEDIUM
A spaceship orbits around a planet at a height of 20 km from its surface. Assuming that only gravitational field of the planet acts on the spaceship, what will be the number of complete revolutions made by the spaceship in 24 hours around the planet?
[Given: Mass of planet  =8×1022 kg ,
Radius of planet =2×106 m,
Gravitational constant  G=6.67×10-11 Nm2/kg2 ]
EASY
Consider two satellites S1 and S2 with periods of revolution 1hr and 8hr respectively revolving around a planet in circular orbits. The ratio of angular velocity of satellite S1 to the angular velocity of satellite S2 is:
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If the axis of rotation of the earth were extended into space then it would pass close to -
EASY
The time period of an earth satellite in circular orbit is independent of
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A remote-sensing satellite of earth revolves in a circular orbit at a height of 0.25×106 m above the surface of earth. If earth's radius is 6.38×106 m and g=9.8 s-2, then the orbital speed of the satellite is:
MEDIUM
The planet Mars has two moons, if one of them has a period 7 hours, 30 minutes and an orbital radius of 9.0×103 km. Find the mass of Mars.
Given 4π2G=6×1011 N-1 m-2 kg2
EASY
When a satellite falls to an orbit of smaller radius its kinetic energy
HARD

The distance between two stars of masses 3MS and 6MS is 9R. Here R is the mean distance between the centres of the Earth and the Sun, and MS is the mass of the Sun. Two stars orbit around their common centre of mass in circular orbits with period nT, whereT is the period of Earth's revolution around the Sun.

The value of n is _____.

EASY
A body is moving in a low circular orbit about a planet of mass M and radius R. The radius of the orbit can be taken to be R itself. Then the ratio of the speed of this body in the orbit to the escape velocity from the planet is: 
MEDIUM
A satellite is revolving in a circular orbit at a height h from the earth's surface (radius of earth R; h << R ). The minimum increase in its orbital velocity required, so that the satellite could escape from the earth's gravitational field, is close to (Neglect the effect of atmosphere.)
EASY
The relative uncertainty in the period of a satellite orbiting around the earth is 10-2 . If the relative uncertainty in the radius of the orbit is negligible, the relative uncertainty in the mass of the earth is: