JEE Questions for Physics Gravitation Quiz 12 - MCQExams.com

One can easily \ weight the earth\ by calculating the mass of earth using the formula (in usual notation)

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Which force in nature exits everywhere?
  • Nuclear force
  • Electromagnetic force
  • Weak force
  • Gravitation
The time period of a simple pendulum on a freely moving artificial satellite is
  • Zero
  • 2 sec
  • 3 sec
  • Infinite
Two planets have the same average density but their radii are R1 and R2. If acceleration due to gravity on these planets be g1 and g2 respectively, then

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An iron ball and a wooden ball of the same radius are released from a height \'h\' in vacuum. The time taken by both of them to reach the ground is
  • Unequal
  • Exactly equal
  • Roughly equal
  • Zero
Read the following statements
S1: An object shall weigh more at pole than at equator when weighed by using a physical balance
S2 : It shall weigh the same at pole and equator when weighed by using a physical balance
S3 : It shall weigh the same at pole and equator when weighed by using a spring balance
S4 :It shall weigh more at the pole than at equator when weighed using a spring balance
Which of the above statements is/are correct?
  • S1 and S2
  • S1 and S4
  • S2 and S3
  • S2 and S4
A man is standing on an international space station, which is orbiting earth at an altitude 520 km with a constant speed 7.6 km/s. If the man\'s weight is 50 kg, his acceleration is
  • 7.6 km/s2
  • 7.6 m/s2
  • 8.4 m/s2
  • 10 m/s2
A body weighs 700 g wt on the surface of the earth. How much will it weigh on the surface of a planet whose mass is 1/7and radius is half that of the earth
  • 200 g wt
  • 400 g wt
  • 50 g wt
  • 300 g wt
As we go from the equator to the poles, the value of g
  • Remains the same
  • Decreases
  • Increases
  • Decreases upto a latitude of 45°
Force of gravity is least at
  • The equator
  • The poles
  • A point in between equator and any pole
  • None of these
The radius of the earth is 6400 km and g = 10 m/sec2.In order that a body of 5 kg weighs zero at the equator, the angular speed of the earth is
  • 1/80 radian/sec
  • 1/400 radian/sec
  • 1/800 radian/sec
  • 1/1600 radian/sec
The value of `g\' at a particular point is 9.8 m/s2.Suppose the earth suddenly shrinks uniformly to half its present size without losing any mass. The value of `g\' at the same point (assuming that the distance of the point from the centre of earth does not shrink) will now be
  • 4.9 m/sec2
  • 3.1 m/sec2
  • 9.8 m/sec2
  • 19.6 m/sec2
If R is the radius of the earth and g the acceleration dueto gravity on the earth\'s surface, the mean density of the earth is
  • 4πG / 3gR
  • 3πR / 4gG
  • 3g / 4πRG
  • πRG / 12G
The radii of two planets are respectively R1 and R2 and their densities are respectively ρ1 and ρ2. The ratio of the accelerations due to gravity at their surfaces is

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    Physics-Gravitation-74772.png

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Spot the wrong statement :
The acceleration due to gravity y decreases if
  • We go down from the surface of the earth towards its centre
  • We go up from the surface of the earth
  • We go from the equator towards the poles on the surface of the earth
  • The rotational velocity of the earth is increased
A spring balance is graduated on sea level. If a body is weighed with this balance at consecutively increasing heights from earth\'s surface, the weight indicated by the balance
  • Will go on increasing continuously
  • Will go on decreasing continuously
  • Will remain same
  • Will first increase and then decrease
The value of g on the earth\'s surface is 980 cm/sec2. Its value at a height of 64 km from the earth\'s surface is
(Radius of the earth R = 6400 kilometers)
  • 960.40 cm/sec2
  • 984.90 cm/sec2
  • 982.45 cm/sec2
  • 977.55 cm/sec2
Choose the correct statement from the following :
Weightlessness of an astronaut moving in a satellite is a situation of
  • Zero g
  • No gravity
  • Zero mass
  • Free fall
If the earth rotates faster than its present speed, the weight of an object will
  • Increase at the equator but remain unchanged at the poles
  • Decrease at the equator but remain unchanged at the poles
  • Remain unchanged at the equator but decrease at the poles
  • Remain unchanged at the equator but increase at the poles
If the earth suddenly shrinks (without changing mass) to half of its present radius, the acceleration due to gravity will be
  • g/2
  • 4 g
  • g/4
  • 2 g
The depth d at which the value of acceleration due to gravity becomes 1/n times the value at the surface, is [R = radius of the earth]

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    Physics-Gravitation-74780.png

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If the density of a small planet is the same as that of earth, while the radius of the planet is 0.2 times that of the earth, the gravitational acceleration on the surfaceof that planet is
  • 0.2 g
  • 0.4 g
  • 2 g
  • 4 g
Let g be the acceleration due to gravity at earth\'s surface and K be the rotational kinetic energy of the earth. Suppose the earth\'s radius decreases by 2% keeping all other quantities same, then
  • g decreases by 2% and K decreases by 4%
  • g decreases by 4% and K increases by 2%
  • g increases by 4% and K increases by 4%
  • g decreases by 4% and K increases by 4%
A body weighs 500 N on the surface of the earth. How much would it weigh half way below the surface of the earth
  • 125 N
  • 250 N
  • 500 N
  • 1000 N
The speed of earth\'s rotation about its axis is o). Its speed is increased to x times to make the effective acceleration due to gravity equal to zero at the equator.Then x is
  • 1
  • 8.5
  • 17
  • 34
If mass of a body is M on the earth surface, then the mass of the same body on the moon surface is
  • M/6
  • Zero
  • M
  • None of these
At what depth below the surface of the earth, acceleration due to gravity g will be half its value 1600 km above the surface of the earth
  • 4.2 × 106 m
  • 3.19 × 106 m
  • 1.59 × 106 m
  • None of these
An object weighs 72 N on earth. Its weight at a height of R/2 from earth is
  • 32 N
  • 56 N
  • 72 N
  • Zero
The angular velocity of the earth with which it has to rotate so that acceleration due to gravity on 60° latitude becomes zero is (Radius of earth = 6400 km. At the poles g = 10 ms–2)
  • 2.5 × 10–3 rad/s
  • 5.0 × 10–1 rad/s
  • 10 × 101 rad/s
  • 7.8 × 10–2 rad/s
Assuming earth to be a sphere of a uniform density, what is the value of gravitational acceleration in a mine 100 km below the earth\'s surface (Given R = 6400 km)
  • 9.66 m/s2
  • 7.64 m/s2
  • 5.06 m/s2
  • 3.10 m/s2
If the mass of earth is 80 times of that of a planet and diameter is double that of planet and \'g\' on earth is 9.8 m/s2, then the value of \'g\' on that planet is
  • 4.9 m/s2
  • 0.98 m/s2
  • 0.49 m/s2
  • 49 m/s2
At what distance from the centre of the earth, the value of acceleration due to gravity g will be half that on the surface (R = radius of earth)
  • 2 R
  • R
  • 1.414 R
  • 0.414 R
A man can jump to a height of 1.5 m on a planet A. What is the height he may be able to jump on another planet whose density and radius are, respectively, one-quarter and one-third that of planet A
  • 1.5 m
  • 15 m
  • 18 m
  • 28 m
The density of a newly discovered planet is twice that of earth. The acceleration due to gravity at the surface of the planet is equal to that at the surface of the earth. If the radius of the earth is R, the radius of the planet would be
  • 2R
  • 4R
  • 1/4 R
  • 1/2 R
If the density of the earth is doubled keeping its radius constant then acceleration due to gravity will be (g = 9.8 m/s2)
  • 19.6 m/s2
  • 9.8 m/s2
  • 4.9 m/s2
  • 2.45 m/s2
If the value of \'g\' acceleration due to gravity, at earth surface is 10 m/s2, its value in m/s2 at the centre of theearth, which is assumed to be a sphere of radius R metre and uniform mass density is
  • 5
  • 10/R
  • 10/2R
  • Zero
Acceleration due to gravity on moon is 1/6 of the acceleration due to gravity on earth. If the ratio of densities of earth (ρe ) and moon (ρm) is (ρe / ρm) = 5/3 then radius of moon Rm in terms of Re will be

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The height from the earth surface at which the value of acceleration due to gravity reduces to 1/4th of its value at earth\'s surface (assume earth to be sphere of radius 6400 km)
  • 1600 km
  • 6400 km
  • 2649 km
  • 2946 km
Acceleration due to gravity is maximum at (R is the radius of earth)
  • A height R/2 from the earth's surface
  • The centre of the earth
  • The surface of the earth
  • A depth R/2 from the earth's surface 2
  • A height R from earth's surface
The mass of diameter of a planet are twice those of earth. The period of oscillation of pendulum on this planet will be (if it is a second\'s pendulum on earth)

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    Physics-Gravitation-74807.png
  • 2 s

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The height at which the weight of a body becomes 1/16th, its weight on the surface of earth (radius R), is
  • 5 R
  • 15 R
  • 3 R
  • 4 R
A spherical planet has a mass Mp and diameter Dp. A particle of mass m falling freely near the surface of this planet will experience an acceleration due to gravity,equal to

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    Physics-Gravitation-74812.png

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The gravitational potential energy of a body of mass \'m\' at the earth\'s surface is –mgRe. Its gravitational potential energy at a height Re from the earth\'s surface will be (Here Re is the radius of the earth)

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    Physics-Gravitation-74817.png

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Escape velocity of a body of 1 kg mass on a planet is 100 m/sec. Gravitational potential energy of the body at the Planet is
  • –5000 J
  • –1000 J
  • –2400 J
  • 5000 J
A body is orbiting very close to the earth surface with kinetic energy KE. The Energy required to completely escape from it is
  • √2 KE
  • KE
  • KE/√2
  • None of these
A body of mass m kg starts falling from a point 2R above the earth\'s surface. Its kinetic energy when it has fallen to a point \'R\' above the earth\'s surface [R–Radius of earth, M–Mass of Earth, G–Gravitational Constant].

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    Physics-Gravitation-74823.png

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A body is projected vertically upwards from the surface of a planet of radius R with a velocity equal to half the escape velocity for that planet. The maximum height attained by the body is
  • R/3
  • R/2
  • R/4
  • R/5
Energy required to move a body of mass m from an orbit of radius 2R to 3R is
  • GMm / 12R2
  • GMm/3R2
  • GMm/8R
  • GMm/6R
Radius of orbit of satellite of earth is R. Its kinetic energy is proportional to

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    Physics-Gravitation-74830.png
  • R

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The escape velocity for a rocket from earth is 11.2 km/sec. Its value on a planet where acceleration due to gravity is double that on the earth and diameter of the planet is twice that of earth will be in km/sec
  • 11.2
  • 5.6
  • 22.4
  • 53.6
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