STD IX 3. The mass of an object is variable.

(a) Only 1 (b) 1 and 3

GRAVITATION (c) 2 and 3 (d) 1 and 2
1. OBJECTIVE QUESTIONS 10. The mass of a body is measured to be 12 kg
on the earth. If it is taken to the moon, its mass
1. Newton’s law of gravitation is valid
will be
(a) on the earth only (b) on the moon only
(a) 12 kg (b) 6 kg
(c) in the laboratory only (d) everywhere
(c) 2 kg (d) 72 kg
2. An astronaut in the orbit in a spacecraft feels
11. A solid of density D is floating in a liquid of
weightlessness
density d. If V is the volume of solid submerged in
(a) due to the absence of gravity inside
the liquid and V’ is the total volume of the solid,
(b) due to the fact that spacecraft has no energy
then V’/ V is equal to
(c) because acceleration in the orbit is equal to
(a) d/D (b) D/d
acceleration of gravity outside
(c) D/ (d + D) (d) (D + d)/D
(d) there is no gravity outside
12. Which of the following statements is true?
3. The equation F r Gm m 2 = 1 2 is valid for
(a) g is same at all places on the surface of earth.
(a) rectangular bodies (b) circular bodies
(b) g has its maximum value at the equator.
(c) elliptical bodies (d) spherical bodies
(c) g is less at the earth’s surface than at a height
4. Newton’s law of gravitation is valid
above it or a depth below it.
(a) in laboratory (b) only on the earth
(d) g is greater at the poles than at the equator.
(c) only in our solar system (d) everywhere
13. If more force is required to bring a body into a
5. When a body is thrown up, the force of gravity
unit acceleration, the body has
is
(a) less mass (b) zero mass (c) more mass
(a) in the upward direction
(d) mass is independent of force
(b) in the downward direction
14. The weight of a body is 120 N on the earth. If
(c) zero (d) in the horizontal direction
it is taken to the moon, its weight will be about
6. When an object is thrown upward, the force of
(a) 120 N (b) 60 N
gravity is
(c) 20 N (d) 720 N
(a) opposite to the direction of motion
15. The value of acceleration due to gravity at the
(b) in the same direction as the direction of
Mount Everest is
motion
(a) g (b) > g (c) < g (d) zero
(c) becomes zero at the highest point
16. Loss of weight of a body immersed in a liquid
(d) increases as it rises up
is
7. What happens to the acceleration due to
(a) equal to the weight of the liquid displaced
gravity with the increase in altitude from the
(b) more than the weight of the liquid displaced
surface of the earth?
(c) less than the weight of the liquid displaced
(a) Increases (b) Decreases
(d) zero
(c) First decreases and then increases
17. The type of force that exists between two
(d) Remains same
charged bodies is
8. The acceleration due to gravity
(a) only gravitational
(a) has the same value everywhere in space
(b) only electrostatic
(b) has the same value everywhere on the earth
(c) neither (a) nor (b)
(c) varies with the latitude on the earth
(d) both (a) and (b)
(d) is greater on the moon due to its smaller
18. Which of the following is correct?
diameter
(a) Weight is a scalar quantity.
9. Which of the following statements is/are
(b) Weight is not a fundamental quantity.
correct?
(c) Weight does not depend on acceleration due
1. Mass of an object is the measure of its inertia.
to gravity.
2. Heavier the object smaller is the inertia.
(d) None of these (a) Kg m3 (b) kg/m3
19. Pascal is a unit of (c) Per m3 (d) It is unitless
(a) pressure (b) force 29. The mass of a body is increased 4fold and
(c) linear momentum (d) energy mass of other body is increased 16fold. How
20. Gravitational force is a should the distance between them be changed to
(a) repulsive force (b) attractive force keep the same gravitational force between them?
(c) neither (a) nor (b) (d) both (a) and (b) (a) 4 times (b) 1/4 times
21. A beaker is filled with a liquid of density d (c) 8 times (d) 1/8 times
upto a height h. If the beaker is at rest, the mean 30. When you put an object on a spring balance,
pressure at the walls is what do you measure?
(a) 0 (b) hdg (c) hdg /2 (d) 2hdg (a) Weight (b) Force
22. A coin and a feather are dropped together in (c) Mass (d) Acceleration
a vacuum. Then 31. Acceleration due to gravity is maximum at (R
(a) the coin will reach the ground first is the radius of earth)
(b) the feather will reach the ground first (a) a height R/2 from the earth’s surface
(c) both will reach the ground at the same time (b) the centre of the earth
(d) the feather will not fall down (c) the surface of the earth
23. “When a solid body is partially or completely (d) a depth R/2 from earth’s surface
immersed in a fluid, the fluid exerts an upward 32. The value of G was first determined
force on the body, whose magnitude is equal to experimentally by
the weight of the displaced fluid”. This is known (a) Newton (b) Henry Cavendish
as (c) Kepler (d) Galileo
(a) Archimedes’ principle (b) Tyndall effect 33. The value of acceleration due to gravity is
(c) Newton’s lst law of motion high if (a) mass and radius both are small
(d) Bernoulli’s theorem (b) mass is small and radius is large
24. Relative density of silver is 10.8. The density (c) mass is large and radius is small
of water 103 Kg/m3. What is the density of silver (d) mass and radius both are large
is SI units? 34. An apple falls towards the earth because the
(a) 10.8 x 108 kg/m3 earth attracts it. The apple also attracts the earth
(b) 12.3 x 108 kg/m3 by the same force. Why do we not see the earth
(c) 10.8 x 102 kg/m3 rising towards the apple?
(d) 11.7 x 108 kg/m3 (a) Acceleration of the earth is very large when
25. Gravitational force is the compared to that of apple.
(a) weakest force (b) Acceleration of the earth is equal to that of
(b) strongest force apple.
(c) short-range force (c) Acceleration of the earth is neither high nor
(d) non-central force too low.
26.The universal constant of gravitation G has the (d) Acceleration of the earth is very small when
unit compared to that of apple.
(a) N (b) m/s2 35. Which of the following is correct for mass?
(c) (N m2)/ kg2 (d) J (a) It is a vector quantity.
27. Where will it be profitable to purchase 1 (b) It is not a fundamental property of material
Kilogram sugar? body.
(a) At poles (c) It is the force with which the earth attracts a
(b) At equator body.
(c) At 45° latitude (d) It is the quantity of matter contained in a body
(d) at 40° latitude 36. The value of g is zero
28. What is the unit of relative density? (a) at the top of the atmosphere
(b) at 20 km below the surface of the earth 3. The force of ........... is the centripetal force on
(c) at 20 km above the surface of the earth the moon.
(d) at the centre of the earth
4. The orbit of a geostationary orbit is
37. In spaceship moving in space, person called ..........
experience
weightlessness as the value of 5. The value of g will become 10% of its value at
(a) mass is zero the earth’s surface at a height ........... above the
(b) acceleration due to gravity is zero surface of earth. Take radius of earth as 6400 km.
(c) gravitational force is zero
(d) none of these 6. The force of gravity between two objects is
38. A balloon of mass m is rising with an inversely proportional to the square of the ...........
acceleration a.
A fraction of its mass is detached from the 7. The acceleration due to gravity at the surface
balloon. Its acceleration will of a planet depends on the .......... and the ..........
(a) decrease (b) increase of the planet.
(c) remain the same (d) none of these
39. The buoyant force on a body acts in a 8. The weight of an object at ........... is zero.
(a) vertically downward direction
(b) vertically upward direction 9. ge and gp denotes the acceleration due to
(c) horizontal direction gravity on the surface of the earth and another
(d) direction between the horizontal and the planet whose mass and radius are twice that of
vertical the earth. The relation that holds is ...........
40. The unit of G/g
(a) kg m-1 (b) kg m-2 10. If the earth rotates faster, the acceleration
(c) m2 kg-1 (d) m kg-1 due to gravity at equator will ...........
41. A piece of iron of density 7.8#103 kg/m3 and
volume 11. Acceleration due to gravity .......... with depth
100 cm3 is totally immersed in water. Calculate below the surface of the earth.
apparent weight in water.
(a) 6.8 N (b) 60 N 12. The constant of gravitation G is related to g
(c) 1.2 N (d) 10 N by .........
42. Orbital velocity of earth satellite does not
depend on 13. Weight of an object is .......... at equator than
(a) mass of the earth at poles.
(b) mass of the satellite
(c) radius of the earth 14. If the density of planet is increased, then the
(d) acceleration due to gravity acceleration due to gravity at its surface
will ...........
2. FILL IN THE BLANK
DIRECTION : Complete the following statements 15. ............ velocity of the planet is constant
with an appropriate word/term to be filled in the when it
blank space (s). revolves in an elliptical orbit around the sun.

1. Acceleration due to gravity is ........... 16. Every object inside the satellite is ..........
proportional to
the density of the planet. 3. TRUE/FALSE
DIRECTION : Read the following statements and
2. Dimensional formula of universal gravitational write your answer as true or false.
constant is ...........
1. The orbit speed of a satellite is inversely
proportional to radius of its orbit.
 1. Assertion: A man is sitting in a boat which
2. For a spherically symmetric earth, the floats on a pond. If the man drinks some water
acceleration due to gravity should be same at the from the pond, the level of water in the pond will
equator and at the poles decrease.
Reason: The weight of the liquid displaced by the
3. An object in a satellite experiences body is greater than the weight of the body.
weightlessness.
2. Assertion: At the centre of earth, a body has a
4. If earth suddenly stops rotating about its axis, centre of mass but no centre of gravity.
then the value of g will be same at all the places. Reason: Acceleration due to gravity at the centre
of the earth is zero.
5. Weightlessness experienced while orbiting the
earth in a spaceship is the result of zero gravity. 3. Assertion: A block of ice with a lead shot
embedded in it floats on water contained in a
6. Force of gravity is least at the equator. vessels. The temperature of the system is kept at
0°C as the ice melts. When ice has melted
7. The gravitation force between a spherical shell completely, water level in the vessel rises.
and a point mass inside it is negative and finite. Reason: The melted ice will raise the water level.
volume or melted ice and lead shot, is equal to
8. It is possible to put on artificial satellite in to the volume of the water displaced when the ice
orbit in such a way that it will remain directly block with lead shot is initially placed in water.
over New Delhi.
4. Assertion: Kepler’s second law of planetary
10. An astronaut cannot use a straw to sip a drink motion is also known as Kepler’s law of areas.
on the surface of the moon. Reason: The line joining the planet and the sun
sweeps equal areas in equal intervals of time.
11. Acceleration due gravity at poles is greater
than that at equator. 5. Assertion: During a journey from the earth to
the moon and back, maximum fuel is spent to
12. Weight of body at centre of the earth is zero. overcome the earth’s gravity at take off.
Reason: Earth’s mass is much greater than that of
13. If the earth stops rotating, acceleration due to the moon.
gravity at poles increases.
6. Assertion: It is the gravitational force exerted
14. Work is to be done on the system of two by the sun and the moon on the sea water that
particles in increasing the distance between causes to the formation of tides in the sea.
them. Reason: Gravitational force of attraction is a
strong force.
4. ASSERTION AND REASON
DIRECTION: In each of the following questions, a 7. Assertion: Any two objects in the universe
statement of Assertion is given and a attract each other by a force called gravitation
corresponding statement of Reason is given just force.
below it. Of the statements, given below, mark Reason: The force of gravitation exerted by the
the correct answer as: earth is called gravity.

(a) Both assertion and reason are true and reason 8. Assertion: Universal gravitational constant G is
is the correct explanation of assertion. a scalar quantity.
(b) Both assertion and reason are true but reason Reason: The value of G is same through out the
is not the correct explanation of assertion. universe.
(c) Assertion is true but reason is false.
(d) Both Assertion and Reason are false.
9. Assertion: An object floats if it displaces an 17. Assertion: By tying a stone to a wooden
amount of liquid whose weight is greater than plank, an object can be made such that it floats in
the actual weight of the object. a river and sinks in the ocean.
Reason: During floatation an object experiences Reason: Density of river water is more than the
no net force in the downward direction. density of sea-water.

10. Assertion: If we drop a stone and a sheet of 18. Assertion: When a body is thrown up, the
paper from a balcony of first floor, then stone will acceleration due to gravity at the topmost point
reach the ground first. is zero.
Reason: The resistance due to air depends on Reason: The acceleration due to gravity is always
velocity only. directed downwards towards the centre of the
earth for a freely falling body.
11. Assertion: The density of a liquid depends
upon the nature and temperature of the liquid. 19. Assertion: An object floats on the surface of a
Reason: The volume of the liquid depends upon liquid in a beaker. The whole system is allowed to
temperature. fall freely under gravity. The upthrust on the
object due to the liquid is equal to the weight of
12. Assertion: When distance between two the liquid displaced.
bodies is doubled and also mass of each body is Reason: Archimedes’ principle states that the
doubled, then the gravitational force between upthrust on an object due to a fluid is equal to
them remains the same. theweight of the fluid displaced.
Reason: According to Newton’s law of
gravitation, product of force is directly 20. Assertion: A sheet of paper falls slower, than
proportional to the product mass of bodies and one that is crumpled in to a ball?
inversely proportional to square of the distance Reason: Sheet of paper has lesser weight than
between them. that is crumpled into a ball.

13. Assertion: The value of the acceleration due

to gravity g on earth depends upon the average
density of the earth.
Reason: It is the radius of the earth which
determines the value of the g.

14. Assertion: The value of acceleration due to

gravity changes with the height, depth and shape
of the earth.
Reason: Acceleration due to gravity is zero at the
centre of the earth.

15. Assertion: When the orbital radius of a planet

is made 4 times, its time period increases by 8
times.
Reason: Greater the height above the earth’s
surface, greater is the time period of revolution.

16. Assertion: Weight of a body on earth is equal

to the force with which the body is attracted
towards the earth.
Reason: Weight of a body is independent of the
mass of the body.