Gravitation : NCERT Exemplar


Multiple Choice Questions

Q.1 Two objects of different masses falling freely near the surface of moon would

 (a) Have same velocities at any instant

(b) Have different accelerations

(c) Experience forces of same magnitude

(d) Undergo a change in their inertia

Sol. (a) 

Q.2 The value of acceleration due to gravity

(a) Is same on equator and poles

(b) Is least on poles

(c) iIs least on equator

 (d) Increases from pole to equator

Sol. (c)

Q.3 The gravitational force between two objects is F. If masses of both objects are halved without changing distance between them, then the gravitational force would become

(a) F/4

(b) F/2

(c) F

(d) 2 F

Sol. (a) 

Q.4 A boy is whirling a stone tied with a string in an horizontal circular path. If the string breaks, the stone

(a) Will continue to move in the circular path

(b) Will move along a straight line towards the centre of the circular path

(c) Will move along a straight line tangential to the circular path

(d) Will move along a straight line perpendicular to the circular path away from the boy

Sol. (c) 

Q.5 An object is put one by one in three liquids having different densities. The object floats with 123, and 9117 parts of their volumes outside the liquid surface in liquids of densities d1, d2 and d3 respectively. Which of the following statement is correct?

(a) d1> d2> d3

(b) d1> d2< d3

(c) d1< d2> d3

(d) d1< d2< d3

Sol. (d) 

Q.6 In the relation F = G M m/d2, the quantity G

(a) Depends on the value of g at the place of observation

(b) Is used only when the earth is one of the two masses

(c) Is greatest at the surface of the earth

(d) Is universal constant of nature

Sol. (d) 

Q.7 Law of gravitation gives the gravitational force between

(a) The earth and a point mass only

(b) The earth and Sun only

(c) Any two bodies having some mass

(d) Two charged bodies only

Sol. (c) 

Q.8 The value of quantity G in the law of gravitation

(a) Depends on mass of earth only

(b) Depends on radius of earth only

(c) Depends on both mass and radius of earth

(d) Is independent of mass and radius of the earth

Sol. (d) 

Q.9 Two particles are placed at some distance. If the mass of each of the two particles is doubled, keeping the distance between them unchanged, the value of gravitational force between them will be

(a) 1/ 4 times

(b) 4 times

(c) 1/ 2 times

(d) Unchanged

Sol. (b) 

Q.10 The atmosphere is held to the earth by

(a) Gravity

(b) Wind

(c) Clouds

(d) Earth’s magnetic field

Sol. (a) 

Q.11 The force of attraction between two unit point masses separated by a unit distance is called

(a) Gravitational potential

(b) Acceleration due to gravity

(c) Gravitational field

(d) Universal gravitational constant

Sol. (d) 

Q.12 The weight of an object at the centre of the earth of radius R is

(a) Zero

(b) Infinite

(c) R times the weight at the surface of the earth

(d) 1/R2 times the weight at surface of the earth

Sol. (a) 

Q.13 An object weighs 10 N in air. When immersed fully in water, it weighs only 8 N. The weight of the liquid displaced by the object will be

(a) 2 N

(b) 8 N

(c) 10 N

(d) 12 N

Sol. (a) 

Q.14 A girl stands on a box having 60 cm length, 40 cm breadth and 20 cm width in three ways. In which of the following cases, pressure exerted by the brick will be

(a) Maximum when length and breadth form the base

(b) Maximum when breadth and width form the base

(c) Maximum when width and length form the base

(d) The same in all the above three cases

Sol. (b) 

Q.15 An apple falls from a tree because of gravitational attraction between the earth and apple. If F1 is the magnitude of force exerted by the earth on the apple and F2 is the magnitude of force exerted by apple on earth, then

(a) F1 is very much greater than F2

(b) F2 is very much greater than F1

(c) F1 is only a little greater than F2

(d) F1 and F2 are equal

Sol. (d)


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