Gravitation CBSE Questions & Answers

Gravitation

This is Physics Class 11 Gravitation CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
The formula for gravitational potential energy associated with two particles of masses \({{\text{m}}_{\text{1}}}\)and \({{\text{m}}_{\text{2}}}\) separated by distance by a distance r is given by
  • A
    \({\rm{v}} = - {{G{m_2}} \over r}\)
  • B
    \({\rm{v}} = - {{G{m_1}{m_2}} \over {2r}}\)
  • C
    \({\rm{v}} = - {{G{m_1}} \over r}\)
  • D
    \({\rm{v}} = - {{G{m_1}{m_2}} \over r}\)
    Correct
2
Escape speed from the earth is the
  • A
    none of these
  • B
    minimum speed at which to throw an object such that it does not fall back to the earth
    Correct
  • C
    minimum speed at which to throw an object such that it falls back to the earth
  • D
    maximum speed at which to throw an object such that it does not fall back to the earth
3
For the earth the escape speed in terms of g the acceleration due to gravity and RE the radius of the earth is
  • A
    \(\sqrt {2g} \)
  • B
    \(\sqrt {2g{R_E}} \)
    Correct
  • C
    \(\sqrt {5g{R_E}} \)
  • D
    \(\sqrt {g{R_E}} \)
4
For earth satellites the centripetal force is provided by
  • A
    gravitational force
    Correct
  • B
    strong interactions
  • C
    electrical forces
  • D
    forces exerted by firing rockets on satellite
5
Time period of an earth satellite very close to the surface of earth h is given by
  • A
    \({T_0} = 2\pi \sqrt {{{{R_E}} \over g}} \)
    Correct
  • B
    \({T_0} = \pi \sqrt {{{{R_E}} \over g}} \)
  • C
    \({T_0} = \pi \sqrt {{{{R_E}} \over {2g}}} \)
  • D
    \({T_0} = \pi \sqrt {{{2{R_E}} \over g}} \)
6
The total energy of a circularly orbiting satellite is
  • A
    positive small
  • B
    zero
  • C
    negative
    Correct
  • D
    positive large
7
for a circularly orbiting satellite the potential energy
  • A
    is negative, and having a magnitude twice that of the negative kinetic energy.
  • B
    is negative, and has a magnitude twice that of the positive kinetic energy.
    Correct
  • C
    is negative, and has a magnitude thrice that of the positive kinetic energy.
  • D
    is negative, and having a magnitude twice that of the positive kinetic energy.
8
For Geostationary Satellites
  • A
    circular orbit is in the equatorial plane of the earth and period of rotation is 14 hrs
  • B
    circular orbit is in the equatorial plane of the earth and period of rotation is 24 hrs
    Correct
  • C
    circular orbit is in the longitudinal plane of the earth and period of rotation is 20 hrs
  • D
    circular orbit is in the equatorial plane of the earth and period of rotation is 34 hrs
9
Geostationary Satellites
  • A
    need more powerful rockets to put them into larger distance orbits
    Correct
  • B
    need less powerful rockets to put them into larger distance orbits
  • C
    are not useful for communication applications
  • D
    need more powerful rockets to put them into smaller distance orbits
10
Polar satellites
  • A
    are low altitude satellites, and go around the poles of the earth in a north-south direction
    Correct
  • B
    are low altitude satellites, and go around the equator of the earth in a north-east direction
  • C
    are high altitude satellites, and go around the equator of the earth in a north-east direction
  • D
    are high altitude satellites, and go around the equator of the earth in a west-east direction
11
Which of the following statements correct?
  • A
    Acceleration due to gravity decreases with increasing altitude.
    Correct
  • B
    The formula –G Mm(1/ \({{\rm{r}}_{\rm{2}}}\) – 1/ \({{\rm{r}}_{\rm{1}}}\)) is less accurate than the formula mg(\({{\rm{r}}_{\rm{2}}}\) – \({{\rm{r}}_{\rm{1}}}\)) for the difference of potential energy between two points \({{\rm{r}}_{\rm{2}}}\)and \({{\rm{r}}_{\rm{1}}}\) distance away from the centre of the earth.
  • C
    Acceleration due to gravity increases with increasing depth (assume the earth to be a sphere of uniform density).
  • D
    Acceleration due to gravity is independent of mass of the earth.
12
Suppose there existed a planet that went around the sun twice as fast as the earth. What would be its orbital size as compared to that of the earth?
  • A
    Larger by a factor of 1.23
  • B
    Smaller by a factor of 0.63
    Correct
  • C
    Larger by a factor of 1.11
  • D
    Smaller by a factor of 0.5
13
A typical adult human has a mass of about 70 kg. (a) What force does a full moon exert on such a human when it is directly overhead with its center 378,000 km away?
  • A
    3.1 \( \times \) \({\rm{1}}{0^{ - {\rm{6}}}}\) N
  • B
    2.4 \( \times \) \({\rm{1}}{0^{ - {\rm{6}}}}\) N
    Correct
  • C
    1.4 \( \times \) \({\rm{1}}{0^{ - {\rm{6}}}}\) N
  • D
    2.0 \( \times \) \({\rm{1}}{0^{ - {\rm{6}}}}\) N
14
A particle of mass 3m is located 1.00 m from a particle of mass m. Where should you put a third mass M so that the net gravitational force on M due to the two masses is exactly zero?
  • A
    0.534 m from the m
  • B
    0.634 m from the m
  • C
    0.634 m from the 3m
    Correct
  • D
    0.234 m from the 3m
15
At what distance above the surface of the earth is the acceleration due to the earth’s gravity 0.980 m/ \({{\rm{s}}^{\rm{2}}}\) if the acceleration due to gravity at the surface has magnitude 9.8 m/ \({{\rm{s}}^{\rm{2}}}\)
  • A
    1.48 \( \times \) \({\rm{1}}{0^{\rm{7}}}\) m
  • B
    0.98 \( \times \) \({\rm{1}}{0^{\rm{7}}}\) m
  • C
    1.38 \( \times \) \({\rm{1}}{0^{\rm{7}}}\) m
    Correct
  • D
    1.18 \( \times \) \({\rm{1}}{0^{\rm{7}}}\) m