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
According to Kepler’s Law of orbits,
  • A
    All planets move in parabolic orbits with the Earth situated at one of the foci of the parabola
  • B
    All planets move in elliptical orbits with the earth situated at one of the foci of the ellipse
  • C
    All planets move in parabolic orbits with the Sun situated at one of the foci of the parabola
  • D
    All planets move in elliptical orbits with the Sun situated at one of the foci of the ellipse
    Correct
2
According to Kepler’s Law of areas,
  • A
    Only the line that joins mars to the earth sweeps equal areas in equal intervals of time
  • B
    The line that joins any planet to the earth sweeps equal areas in equal intervals of time
  • C
    Only the line that joins earth to the sun sweeps equal areas in equal intervals of time
  • D
    The line that joins any planet to the sun sweeps equal areas in equal intervals of time
    Correct
3
According to Kepler’s Law of periods,
  • A
    The cube of the time period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse traced out by the planet
  • B
    The square of the time period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse traced out by the planet.
    Correct
  • C
    The square of the time period of revolution of a planet is proportional to the cube of the semi-minor axis of the ellipse traced out by the planet
  • D
    The cube of the time period of revolution of a planet is proportional to the square of the semi-major axis of the ellipse traced out by the planet
4
The area \(\Delta \)A swept out by a planet of mass m in time interval \(\Delta \)t is related to the angular momentum by (g is acceleration due to gravity and G is the universal gravitational constant)
  • A
    \(\Delta {\bf{A}}/\Delta {\rm{t}}\) = 2L / m
  • B
    \(\Delta {\bf{A}}/\Delta {\rm{t}}\) = gL / (2 m)
  • C
    \(\Delta {\bf{A}}/\Delta {\rm{t}}\) = GL / (2 m)
  • D
    \(\Delta {\bf{A}}/\Delta {\rm{t}}\) = L / (2 m)
    Correct
5
Newton’s law of universal gravitation states that the gravitational force of attraction between any two particles of masses m1 and m2 separated by a distance r has the magnitude
  • A
    \({\rm{F}} = {\rm{G}}{{{{\rm{m}}_2}} \over {{{\rm{r}}^2}}}\)
  • B
    \({\rm{F}} = {\rm{G}}{{{{\rm{m}}_1}{{\rm{m}}_2}} \over {{{\rm{r}}^2}}}\)
    Correct
  • C
    \({\rm{F}} = {{{{\rm{m}}_1}{{\rm{m}}_2}} \over {{{\rm{r}}^2}}}\)
  • D
    \({\rm{F}} = {\rm{G}}{{{{\rm{m}}_1}} \over {{{\rm{r}}^2}}}\)
6
The direction of the universal gravitational force between particles of masses \({{\rm{m}}_{\rm{1}}}\) and \({{\rm{m}}_{\rm{2}}}\)
  • A
    directed towards the center of the earth
  • B
    directed towards \({{\rm{m}}_{\rm{1}}}\)
  • C
    directed towards \({{\rm{m}}_{\rm{2}}}\)
  • D
    directed towards \({{\text{m}}_{\text{2}}}\) on \({{\text{m}}_{\text{1}}}\) and directed towards \({{\rm{m}}_{\rm{1}}}\) on \({{\rm{m}}_{\rm{2}}}\)
    Correct
7
A ‘central’ force is always directed
  • A
    along the position vector of the point of application of the force with respect to the fixed point
    Correct
  • B
    perpendicular to the position vector of the point of application of the force with respect to the fixed point
  • C
    at a varying angle to the position vector of the point of application of the force with respect to the fixed point
  • D
    at a fixed angle to the position vector of the point of application of the force with respect to the fixed point
8
Gravitational force on point mass m1 is
  • A
    the vector sum of the gravitational forces exerted by \({{\rm{m}}_{\rm{2}}}\), \({{\rm{m}}_{\rm{3}}}\) and \({{\rm{m}}_{\rm{4}}}\)
    Correct
  • B
    the difference of gravitational forces exerted by \({{\rm{m}}_{\rm{4}}}\), \({{\rm{m}}_{\rm{3}}}\) and \({{\rm{m}}_{\rm{2}}}\)
  • C
    the scalar sum of the gravitational forces exerted by \({{\rm{m}}_{\rm{2}}}\), \({{\rm{m}}_{\rm{3}}}\) and \({{\rm{m}}_{\rm{4}}}\)
  • D
    the difference of gravitational forces exerted by \({{\rm{m}}_{\rm{2}}}\), \({{\rm{m}}_{\rm{3}}}\) and \({{\rm{m}}_{\rm{4}}}\)
9
To find the resultant gravitational force acting on the particle m due to a number of masses we need to use
  • A
    the principle of no action
  • B
    the principle of least action
  • C
    the principle of superposition
    Correct
  • D
    the principle of maximal action
10
The force of attraction between a hollow spherical shell of uniform density and a point mass situated outside is just as if the entire mass of the shell is
  • A
    concentrated at the centre of the shell.
    Correct
  • B
    equally concentrated at three points on a triangle of the shell.
  • C
    equally concentrated at opposite ends of the diameter of the sphere
  • D
    equally concentrated at four points on a square of the shell.
11
The force of attraction due to a hollow spherical shell of uniform density, on a point mass situated inside it is
  • A
    none of these
  • B
    zero
    Correct
  • C
    negative
  • D
    positive
12
In Cavendish’s experiment,
  • A
    torque on bar AB having two small lead spheres due to gravitational forces is balanced by the restoring torque of the wire
    Correct
  • B
    net force on bar AB having two small lead spheres due to gravitational forces is negative
  • C
    net torque on bar AB having two small lead spheres due to gravitational forces is positive
  • D
    net force on bar AB having two small lead spheres due to gravitational forces is positive
13
The value of the gravitational constant G is
  • A
    G = 6.67\( \times \)\({\rm{1}}{0^{ - {\rm{11}}}}\) N m\(^{\rm{2}}\)/kg
  • B
    G = 6.67\( \times \)\({\rm{1}}{0^{ - {\rm{11}}}}\)N m\(^{\rm{2}}\)/kg\(^{\rm{2}}\)
    Correct
  • C
    G = 6.67\( \times \)\({\rm{1}}{0^{ - {\rm{11}}}}\) m\(^{\rm{2}}\)/kg\(^{\rm{2}}\)
  • D
    G = 6.67\( \times \)\({\rm{1}}{0^{ - {\rm{11}}}}\) N m/kg\(^{\rm{2}}\)
14
The acceleration due to gravity at a height h in terms of mass of earth \({{\text{M}}_{\text{E}}}\) and radius of the earth \({{\rm{R}}_{\rm{E}}}\) and gravitational constant G is
  • A
    \(g\left( h \right) = {{G{M_E}} \over {{{\left( {{R_E} + h} \right)}^2}}}\)
    Correct
  • B
    \(g\left( h \right) = {{{M_E}} \over {{{\left( {{R_E} + h} \right)}^2}}}\)
  • C
    \(g\left( h \right) = {{G{M_E}} \over {{{\left( {{R_E} + 2h} \right)}^2}}}\)
  • D
    \(g\left( h \right) = {{Gm{M_E}} \over {{{\left( {{R_E} + h} \right)}^2}}}\)
15
The acceleration due to gravity at a depth d in terms of g the acceleration due to gravity at radius of the earth \({{\rm{R}}_{\rm{E}}}\) and \({{\rm{R}}_{\rm{E}}}\) is
  • A
    \(g\left( d \right) = g\left( {1 + d/{R_E}} \right)\)
  • B
    \(g\left( d \right) = g\left( {1 - d/{R_E}} \right)\)
    Correct
  • C
    \(g\left( d \right) = g\left( {1 + d/{R_E}} \right)\)
  • D
    \(g\left( d \right) = g\left( {1 - 2d/{R_E}} \right)\)