Gravitation

Gravitation

Easy Questions
Moderate Questions

Mechanics

Physical World, Units and Measurements
Motion in a Straight Line
Motion in a Plane
Laws of Motion
Work, Energy and Power
Gravitation
Mechanical Properties of Solids
Mechanical Properties of Fluids
System of Particles and Rotational Motion
  1. A geostationary satellite is orbiting the earth at a height of 5R above that surface of the earth, R being the radius of the earth. The time period of another satellite in hours at a height of 2R from the surface of the earth is :








  1. View Hint View Answer Discuss in Forum

    ​According to Kelpner’s law of period T2 ∝ R3

    T12
    		 =
    R13
    		 =
    (6R)3
    		 = 8
    T22R23(3R)3

    24 × 24
    		 = 8
    T22

    T22 =
    24 × 24
    		 = 72 = 36 × 2
    8

    T2 = 6 √2

    Correct Option: C

    ​According to Kelpner’s law of period T2 ∝ R3

    T12
    		 =
    R13
    		 =
    (6R)3
    		 = 8
    T22R23(3R)3

    24 × 24
    		 = 8
    T22

    T22 =
    24 × 24
    		 = 72 = 36 × 2
    8

    T2 = 6 √2

  1. A particle of mass ‘m’ is kept at rest at a height 3R from the surface of earth, where ‘R’ is radius of earth and ‘M’ is mass of earth. The minimum speed with which it should be projected, so that it does not return back, is (g is acceleration due to gravity on the surface of earth)








  1. View Hint View Answer Discuss in Forum

    As we know, the minimum speed with which a body is projected so that it does not return back is called escape speed.

    =
    GM
    		1 / 2 (∵ h = 3R)
    6400

    Correct Option: B

    As we know, the minimum speed with which a body is projected so that it does not return back is called escape speed.

    =
    GM
    		1 / 2 (∵ h = 3R)
    6400

  1. The radius of a planet is twice the radius of earth. Both have almost equal average mass-densities. If VP and VE are escape velocities of the planet and the earth, respectively, then








  1. View Hint View Answer Discuss in Forum

    Escape velocity, Ve = R √(8 / 3) π GP

    ⇒ Ve ∝ R ⇒
    VP
    		 =
    RP
    		 = 2
    VERE

    ⇒ VP = 2 VE

    Correct Option: C

    Escape velocity, Ve = R √(8 / 3) π GP

    ⇒ Ve ∝ R ⇒
    VP
    		 =
    RP
    		 = 2
    VERE

    ⇒ VP = 2 VE

  1. 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 × 1066 m and g = 9.8 ms–2, then the orbital speed of the satellite is :​​​








  1. View Hint View Answer Discuss in Forum

    Given : Height of the satellite from the earth's surface h = 0.25 × 106m ​
    Radius of the earth R = 6.38 × 106m ​
    Acceleration due to gravity g = 9.8 m/s2 ​
    Orbital velocity, Vo = ?

    = 7.76 km/s ∵
    GM
    		 = g
    R2

    Correct Option: D

    Given : Height of the satellite from the earth's surface h = 0.25 × 106m ​
    Radius of the earth R = 6.38 × 106m ​
    Acceleration due to gravity g = 9.8 m/s2 ​
    Orbital velocity, Vo = ?

    = 7.76 km/s ∵
    GM
    		 = g
    R2

  1. 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,​​​








  1. View Hint View Answer Discuss in Forum

    The gravitational force on the satellite will be aiming towards the centre of the earth so acceleration of the satellite will also be aiming towards the centre of the earth.

    Correct Option: C

    The gravitational force on the satellite will be aiming towards the centre of the earth so acceleration of the satellite will also be aiming towards the centre of the earth.