## Chapter 3 Gravitation Multiple Choice Question And Answers

**Direction:** Choose the correct option for each questions. There is only one correct response for each question.

**Question 1. Choose the unit of relative density.**

- kg
- G
- Newton
- None of the above

**Answer.** 4. None of the above

**Question 2. The S.I. unit of thrust is ______.**

- Newton
- m/s
- Dyne
- pascal

**Answer.** 1. Newton

**Question 3. ______ is the quantity of matter contained in the body.**

- Weight
- Mass
- Acceleration
- Force

**Answer.** 2. Mass

**Question 4. The value of gravitational constant is ______**

- 6.6734 × 10
^{-11}N m^{2}/kg^{2} - 7.6734 × 10
^{-10}N m^{2}/kg^{2} - 8.6734 × 10
^{-11}N m/kg^{2} - 9.6734 × 10
^{-11}N m^{2}/kg

**Answer.** 1. 6.6734 × 10^{-11} N m^{2}/kg^{2}

**Question 5. When an object is thrown up, the force of gravity ______.**

- Increases as it rises up
- Becomes zero at the highest point
- Is opposite to the direction of motion
- Is in the same direction as the direction of motion

**Answer.** 3. Is opposite to the direction of motion

**Read and Learn More ****NEET Foundation Multiple Choice Questions**

**Question 6. The acceleration due to gravity is zero at ______**

- Poles
- Centre of earth
- Equator
- Sea level

**Answer.** 2. Centre of earth

**Question 7. Mass of a body is ______ throughout the universe.**

- Constant
- Variable
- Zero
- Negative

**Answer.** 1. Constant

**Question 8. ______ is the thrust per unit area of surface.**

- Speed
- Velocity
- Pressure
- Acceleration

**Answer.** 3. Pressure

**Question 9. The gravitational force between two bodies is ______.**

- Always attractive
- Always repulsive
- Attractive only at large distance
- Repulsive only at large distance

**Answer.** 1. Always attractive

**Question 10. There is no atmosphere on the moon because**

- It revolves round the earth.
- It is closer to the earth.
- The escape velocity of moon is less than root mean square velocity of gas molecule here.
- It is far away from the sun.

**Answer.** 3. The escape velocity of moon is less than root mean square velocity of gas molecule here.

**Question 11. The upward force acting on an object submerged in a liquid is called ______.**

- Pressure
- Force of friction
- Thrust
- Buoyant force

**Answer.** 4. Buoyant force

**Question 12. Gravitational force is responsible for ______.**

- Keeping plants in their rad2
- Keeping animals in their rad2.
- Keeping plants on theft axes
- For the motion of planets around the sun

**Answer.** 4. For the motion of planets around the sun

**Question 13. The value of g decreases with ______.**

- Speed
- Altitude
- Acceleration
- Velocity

**Answer.** 2. Altitude

**Question 14. The distance from the centre of the earth to the centre of the moon is called as ______.**

- Orbital radius of the moon
- Orbital length of the earth
- Orbital radius of the earth
- Orbital length of the moon

**Answer.** 1. Orbital radius of the moon

**Question 15. The weight of an object in a satellite orbiting around the earth is ______.**

- Less than the actual weight
- Greater than the actual weight
- Zero
- Actual weight

**Answer.** 3. Zero

**Question 16. The acceleration of the moon is because of the ______**

- Gravitational force exerted by the planets.
- Gravitational force exerted on the moon by the earth.
- Gravitational force exerted on the earth by the moon.
- Gravitational force exerted by the sun.

**Answer.** 2. Gravitational force exerted on the moon by the earth.

**Question 17. Larger the volume of an object submerged in a fluid, greater is the ______.**

- Gravity
- Upthrust.
- Mass
- Pressure

**Answer.** 2. Upthrust.

**Question 18. Any substance that can flow is called ______.**

- Solid
- Liquid
- Fluid
- Gas

**Answer.** 3. Fluid

**Question 19. Buoyancy is denoted by the symbol ______.**

- F
_{A} - F
_{B} - F
_{C} - F
_{D}

**Answer.** 2. F_{B}

**Question 20. Acceleration due to Gravity (g) on the surface of earth at poles is ______.**

- Maximum
- Minimum
- Zero
- Same as that on equator

**Answer.** 1. Maximum

**Question 21. The unit of (g) – acceleration due to Gravity, is ______.**

- N m/s²
- N m/s
- m/s²
- kg m/s

**Answer.** 3. N m/s²

**Question 22. In order to derive the law of gravitation, Newton assumed that the moon’s orbit is ______.**

- Straight
- Parabolic
- Uniform
- Circular

**Answer.** 4. Circular

**Question 23. The equation for the mass of the earth (ME) is ______.**

- M
_{E}= R E^{2}g/G - M
_{E}= R E^{4}g/G - M
_{E}= RG E^{2}/g - M
_{E}= R g E^{2}/G

**Answer.** 1. M_{E} = R E^{2} g/G

**Question 24. If the density of an object is more than the density of the liquid, then it ______ in the liquid.**

- Floats
- Sinks
- Oscillates
- Jumps

**Answer.** 2. Sinks

**Question 25. A fluid contained in a vessel exerts pressure in ______.**

- All directions
- Downwards
- Upwards
- Sideways

**Answer.** 1. All directions

**Question 26. The S.I. unit of pressure is ______.**

- newton
- dyne
- pascal
- metre

**Answer.** 3. pascal

**Question 27. As per Newton, the force of attraction (F) between two particles is ______**

- Directly proportional to the product of their masses
- Inversely proportional to the square of distance between the particles
- Both are correct
- None of the Above

**Answer.** 3. Both are correct

**Question 28. The ______ is the measure of its inertia.**

- Mass
- Velocity
- Height
- Distance

**Answer.** 1. Mass

**Question 29. Choose the incorrect statement related to laws of liquid pressure**

- Pressure at a point inside the liquid increases with the depth from its free surface.
- In a stationary liquid, pressure is same at all the points on a horizontal plane.
- Pressure is different in all the directions about a point in liquid.
- Pressure at same depth is in different liquids.

**Answer.** 3. Pressure is different in all the directions about a point in liquid.

**Question 30. Pressure is a ______ quantity.**

- Scalar
- Vector
- Both
- None of the above

**Answer.** 1. Scalar

**Question 31. If mass is more, inertia will be ______.**

- Less
- More
- Equal
- Independent

**Answer.** 2. More

**Question 32. The force (F) on a body due to earth’s gravity is ______.**

- mg
- mg/2
- m/g
- m/2g

**Answer.** 1. mg

**Question 33. The value of g on moon’s surface is nearly ______.**

- one-third of the value of g on earth’s surface
- one-fourth of the value of g on earth’s surface
- one-sixth of the value of g on earth’s surface
- one-eight of the value of g on earth’s surface

**Answer.** 3. one-sixth of the value of g on earth’s surface

**Question 34. Force due to gravity acts ______.**

- Vertically downwards at the centre of gravity of the object
- Vertically upwards at the centre of gravity of the object
- in all the directions
- None of the Above

**Answer.** 1. Vertically downwards at the centre of gravity of the object

**Question 35. Archimedes’ principle is applicable for ______.**

- Solid
- Liquid
- Gas
- All of the above

**Answer. **

2. Liquid

3. Gas

**Question 36. The magnitude of upthrust on an object due to liquid depends on the ______.**

- Volume of object submerged in the liquid
- Density of the liquid in which the object is submerged
- Volume of object above the liquid
- Density of the solid

**Answer.**

- Volume of object submerged in the liquid
- Density of the liquid in which the object is submerged

**Question 37. The pressure at a point inside a liquid depends on ______.**

- Depth of the point below the free surface
- Density of liquid
- Acceleration due to gravity
- Surface area of liquid

**Answer.**

- Depth of the point below the free surface
- Density of liquid
- Acceleration due to gravity

**Question 38. The universal law of gravitation is**

- The force that binds us to the earth.
- The motion of the moon around the earth.
- The motion of planets around the sun.
- The tides due to the moon and the sun.

**Answer. **

- The force that binds us to the earth.
- The motion of the moon around the earth.
- The motion of planets around the sun.
- The tides due to the moon and the sun.

**Question 39. The force of attraction (F) between two particles is ______.**

- Directly proportional to the product of their masses
- Inversely proportional to the product of their masses
- Directly proportional to the square of distance between them
- Inversely proportional to the square of distance between them

**Answer.**

1. Directly proportional to the product of their masses

4. Inversely proportional to the square of distance between them

**Question 40. Choose the correct statement**

- The weight of an object is the force with which the earth attracts the object.
- The weight of an object is the force with which the earth repels the object.
- Weight is a vector quantity.
- Weight is a scalar quantity.

**Answer.**

1. The weight of an object is the force with which the earth attracts the object.

4. Weight is a scalar quantity.

**Question 41. Choose the incorrect statement**

- Relative density of a substance is defined as the ratio of mass of the substance to the mass of an equal volume of water at 4°C.
- Relative density (R.D.) of a substance is the ratio of the density of that substance to the density of water at 4°C.
- Unit of relative density is Newton.
- Unit of relative density is Dyne.

**Answer.**

3. Unit of relative density is Newton.

4. Unit of relative density is Dyne.

**Question 42. Characteristic properties of upthrust are _____.**

- Larger the volume of object submerged in fluid, smaller is the upthrust.
- Larger the volume of object submerged in fluid, greater is the upthrust.
- For same volume inside the fluid more the density of fluid, greater is the upthrust.
- The upthrust acts on an object in upward direction at the centre of buoyancy.

**Answer.**

2. Larger the volume of object submerged in fluid, greater is the upthrust.

3. For same volume inside the fluid more the density of fluid, greater is the upthrust.

4. The upthrust acts on an object in upward direction at the centre of buoyancy.

**Question 43. Choose the incorrect statement**

- The normal force per unit area is called pressure.
- The normal force per unit area is called thrust.
- The normal force per unit area is called density.
- The normal force per unit area is called upthrust.

**Answer.**

2. The normal force per unit area is called thrust.

3. The normal force per unit area is called density.

4. The normal force per unit area is called upthrust.

**Question 44. Choose the correct statement**

- Pressure = Thrust/Area
- Pressure is a scalar quantity
- Pressure is a vector quantity
- Pressure = Distance/Time

**Answer. **

- Pressure = Thrust/Area
- Pressure is a scalar quantity

**Question 45. The mass of earth is 6 × 10 ^{24} kg and radius of earth is 6.4 × 10^{6} m. The magnitude of force between the mass of 1 kg and the earth is:**

- 9.770 N
- 9.810 N
- 9.830 N
- 9.790 N

**Answer.** 1. 9.770 N

**Question 46. With the increase in the density of a fluid, the upthrust experienced by a body immersed in it is**

- decreases
- increases
- remains same
- none of these

**Answer.** 2. increases

**Question 47. The acceleration due to gravity on earth is 9.81 ms ^{-2}. If the acceleration due to gravity on the surface of moon is 1/6 of the earth, the weight of 10 kg mass on moon is:**

- 1.67 N
- 16.35 N
- 17.50 N
- None of these

**Answer.** 2. 16.35 N

**Question 48. The apparent weight of a body in a fluid is:**

- equal to weight of fluid displaced
- volume of fluid displaced
- difference between its weight in air and weight of fluid displaced
- none of the above

**Answer.** 3. difference between its weight in air and weight of fluid displaced

**Question 49. The average distance between the earth and moon is 3.84 × 10 ^{5} km. If the mass of moon is 7.4 × 10^{22} kg and that of earth is 6 × 10^{24} kg, the gravitational force of the moon on the earth is:**

- 2.01 × 10
^{20}N - 20.1 × 10
^{21}N - 20.1 × 10
^{20}N - none of these

**Answer.** 1. 2.01 × 10^{20} N

**Question 50. The phenomenon due to which a solid expereinces upward force when immersed in water is called:**

- floatation
- buoyancy
- density
- none of these

**Answer.** 2. buoyancy

**Question 51. The mass of earth is 6 × 10 ^{24} kg, radius 6.4 × 10^{6} m and G = 6.7 × 10^{-11} Nm^{2} kg^{-2}. The acceleration due to gravity on the surface of earth is:**

- 9.70 ms
^{-2} - 9.78 ms
^{-2} - 9.89 ms
^{-2} - 9.80 ms
^{-2}

**Answer.** 4. 9.80 ms^{-2}

**Question 52. The radius of earth is 6400 km and value of ‘g’ at its surface is 9.8 ms ^{-2}. The value of ‘g’ at a height of 12,800 km will be:**

- 5.07 ms
^{-2} - 1.09 ms
^{-2} - 3.09 ms
^{-2} - 4.08 ms
^{-2}

**Answer.** 2. 1.09 ms^{-2}

**Question 53. If ‘g’ = 9.8 ms ^{-2}, the weight of body of mass 10 kg is:**

- 138 N
- 158 N
- 98 N
- 78 N

**Answer.** 3. 98 N

**Question 54. Imagine a heavenly body which has a mass twice of the earth and radius thrice of the earth. If a stone on earth weighs 900 N, its weight on the heavenly is:**

- 200 N
- 600 N
- 400 N
- 500 N

**Answer.** 1. 200 N

**Question 55. Two neutrons of mass 1.67 × 10 ^{-27} kg are at distance of 10^{-15} m from each other. The gravitational force of attraction between them is:**

- 4.86 × 10
^{-34}N - 5.86 × 10
^{-34}N - 1.86 × 10
^{-34}N - 2.86 × 10
^{-34}N

**Answer.** 3. 1.86 × 10^{-34} N

**Question 56. A spaceship is orbiting around the earth at height twice the radius of earth. If ‘g’ on earth is 9.8 ms ^{-2}, the ‘g’ at the height is:**

- 2.1 ms
^{-2} - 5.1 ms
^{-2} - 3.1 ms
^{-2} - 1.1 ms
^{-2}

**Answer.** 4. 1.1 ms^{-2}

**Question 57. The mass and radius of earth is 6 × 10 ^{24} kg and 6400 km. If another heavenly body has half the mass and the radius of earth, the value of g on it will be:**

- 4.96 ms
^{-2} - 19.6 ms
^{-2} - 29.6 ms
^{-2} - 39.6 ms
^{-2}

**Answer.** 2. 19.6 ms^{-2}

**Question 58. The radius of moon is 0.27 times the radius of earth, whereas of g**_{moon }**is 1.27 ms ^{-2} and g_{earth} is 9.8 ms^{-2}. The ratio of mass of earth to the mass of moon is:**

- 46 times
- 58 times
- 79 times
- 67 times

**Answer.** 3. 79 times

**Question 59. The weight of body on the surface of earth is 90 kgf. Its weight on the surface of another planet of mass 1/9 and radius half on the earth will be:**

- 40 kgf
- 30 kgf
- 35 kgf
- 50 kgf

**Answer.** 1. 40 kgf

**Question 60. When an object sinks in a liquid its:**

- buoyant force is more than the weight of object
- buoyant force is less than the weight of object
- buoyant force is equal to the weight of object
- none of the above

**Answer.** 2. buoyant force is less than the weight of object

**Question 61. If the diameter of earth becomes 3 times its present value, but mass does not change, the weight of an object will decrease to:**

- \(\frac{1}{3} \text { th }\)
- \(\frac{1}{6} \text { th }\)
- \(\frac{1}{8} \text { th }\)
- \(\frac{1}{9} \text { th }\)

**Answer.** 4. \(\frac{1}{9} \text { th }\)

**Question 62. A glass stopper suspended form the hook of a spring balance and immersed completely in water reads Wgf. If the same stopper is immersed in** **alcohol (density 0.80 gcm ^{-3}), the reading on the spring balance will be:**

- less than Wgf
- more than Wgf
- Wgf
- none of these

**Answer.** 2. more than Wgf

**Question 63. The value of ‘g’ on the top of Mount Everest (height 8848 m) will be:**

- 9.77 ms
^{-2} - 6.77 ms
^{-2} - 6.67 ms
^{-2} - 5.77 ms
^{-2}

**Answer.** 1. 9.77 ms^{-2}

**Question 64. The radius of earth is 6400 km. The value of ‘g’ will be 60% at the height of:**

- 5.76 × 10
^{3}km - 1.86 × 10
^{3}km - 1.47 × 10
^{3}km - 3.86 × 10
^{3}km

**Answer.** 2. 1.86 × 10^{3} km

**Question 65. If radius of earth is R, at what height from the surface of earth the weight becomes half:**

- 0.414
- 0.518 R
- 0.514 R
- 0.314 R

**Answer.** 1. 0.414

**Question 66. Thrust acting perpendicularly on the unit surface area is called:**

- pressure
- moment of force
- down thrust
- none of these

**Answer.** 1. pressure

**Question 67. The pressure exerted on a given surface is:**

- directly proportional to the force acting on the surface
- directly proportional to area of crosssection of surface
- inversely proportional to area of crosssection of surface
- both (a) and (c)

**Answer.** 4. both (a) and (c)

**Question 68. Your weight recorded by an accurate weighing machine is 42 kgf. In actual practice your weight is:**

- more than 42 kgf
- less than 42 kgf
- 42 kgf
- none of these

**Answer.** 1. more than 42 kgf

**Question 69. One pascal is equal to:**

- N cm
^{-2} - Nm
^{-2} - Nm2
- Nm
^{-1}

**Answer.** 2. Nm^{-2}

**Question 70. Tank trailors are provided with 16 wheels so as to:**

- increase pressure on the road
- decrease pressure on the road
- support the weight of the tank
- none of the above

**Answer.** 2. decrease pressure on the road

**Question 71. Pressure applied on liquids is transmitted with undiminished force:**

- in downward direction only
- upward direction only
- sides of containing vessel
- in all directions

**Answer.** 4. in all directions

**Question 72. The knives are often sharpened:**

- to decrease the area of cutting edge and hence increasing pressure
- to decrease the area of cutting edge and hence decreasing pressure
- to give it a shine
- none of the above

**Answer.** 1. to decrease the area of cutting edge and hence increasing pressure

**Question 73. The strap of a school bag is not made of thin string, because:**

- string is likely to break
- string has less area of cross-section and hence exerts less pressure on shoulder
- string has less area of cross-section and hence exerts more pressure on shoulder
- none of the above

**Answer.** 3. string has less area of cross-section and hence exerts more pressure on shoulder

**Question 74. When a body is wholly or partially immersed in a liquid it experiences a buoyant force which is equal to the:**

- volume of liquid displaced by it
- weight of liquid displaced by it
- both (a) and (b)
- none of the (a) or (b)

**Answer.** 2. weight of liquid displaced by it

**Question 75. The relative density of zinc metal is 4.2. Its density in SI system is:**

- 4.2 kg m
^{-3} - 42 kg m
^{-3} - 420 kg m
^{-3} - 4200 kg m
^{-3}

**Answer.** 4. 4200 kg m^{-3}

**Question 76. Which is incorrect statement?**

- tides are formed in the sea due to gravitational pull of the sun and moon.
- earth holds atmosphere on account of gravitational pull of earth.
- hydrogen filled balloons rise up because, no gravitational pull acts on it
- gravitational pull of the earth keeps us and other objects firmly on ground

**Answer.** 3. hydrogen filled balloons rise up because, no gravitational pull acts on it

**Question 77. Two similar sheets of a paper Aand B are taken. The sheet B is crumpeld to form a ball. Both A and B are allowed to fall from a height of 10 m.**

- both A and B will reach ground at the same time.
- A will reach earlier than B.
- B will reach earlier than A
- none of the above

**Answer.** 3. B will reach earlier than A

**Question 78. A stone is released from the top of tower 19.6m high. If ‘g’ is 9.8 ms ^{-2}, the final velocity of the stone on reaching the ground is:**

- 9.8 ms
^{-1} - 28.4 ms
^{-1} - 19.6 ms
^{-1} - none of these

**Answer.** 3. 19.6 ms^{-1}

**Question 79. A stone is thrown vertically upward with an initial velocity of 40 ms ^{-1}. Taking g = 10 ms^{-2}, the maximum displacement and distance covered by the stone on reaching ground is:**

- displacement: zero; distance = 80 m
- displacement: zero; distance covered = 160 m
- displacement = 80 m; distance = 160
- distance and displacement = 180 m.

**Answer.** 2. displacement: zero; distance covered = 160 m

**Question 80. A cricket ball is vertically thrown upward, which rises to the height of 10 m. If g = 10 ms ^{-2}, the time in which it rises up to the maximum height is:**

- 1.53 s
- 1.63 s
- 1.55 s
- 1.43 s

**Answer.** 1. 1.53 s

**Question 81. A plastic ball released under water comes up. It is because the weight of the plastic ball is:**

- equal to the weight of water displaced by it.
- less than the weight of water displaced by it.
- more than the weight of water displaced by it.
- none of the above

**Answer.** 2. less than the weight of water displaced by it.

**Question 82. A body has density 9.6 gcm ^{-3}. Its density in SI system is:**

- 96 kgm
^{-3} - 960 kgm
^{-3} - 9600 kgm
^{-3} - 96,000 kgm
^{-3}

**Answer.** 3. 9600 kgm^{-3}

**Question 83. A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upward from the ground with a velocity of 25 ms ^{-1}. If g = 10 ms^{-2}, the stones will meet at:**

- 25 m from ground after 5 s (g = 10 ms–2)
- 20 m from ground after 4 s
- 20 m from ground after 4.5 s
- 20 m from ground after 3.8 s

**Answer.** 2. 20 m from ground after 4 s

**Question 84. The SI unit of relative density is:**

- kgm
^{-3} - gcm
^{-3} - kgcm
^{-3} - no unit

**Answer.** 4. no unit

**Question 85. A stone thrown vertically upward returns back to the thrower in 6 sec. The maximum height attained by the stone is:**

- 25 m
- 35 m
- 40 m
- 45 m

**Answer.** 4. 45 m

**Question 86. The pressure exerted by 50 kg (g = 10 ms ^{-2}) on an area of cross-section of 2 m^{2} is:**

- 50 Pa
- 200 Pa
- 250 Pa
- 1000 Pa

**Answer.** 3. 250 Pa

**Question 87. A truck is of mass 50,000 kg (g = 10 ms ^{-2}), its tyres exert a pressure of 2,500,000 Pa. The surface area of tyres in contact with ground is:**

- 2 m
^{2} - 0.2 m
^{2} - 2.5 m
^{2} - 2.75 m
^{2}

**Answer.** 2. 0.2 m^{2}

**Question 88. The force experienced by a body when partially or fully immersed in water is called:**

- apparent weight
- upthrust
- down thrust
- none of these

**Answer.** 2. upthrust

**Question 89. When a body is floating in a liquid:**

- the weight of body is less than the upthrust due to immersed part of body
- the weight of body is more than the upthrust due to immersed part of body
- the weight of body is equal to the upthrust due to immersed part of body
- none of the above

**Answer.** 3. the weight of body is equal to the upthrust due to immersed part of body

## Chapter 3 Gravitation Free Fall

**Question 1. ______ is a natural phenomenon in which two objects having masses attract towards each other.**

- Gravitation
- Speed
- Velocity
- Acceleration

**Answer.** 1. Gravitation

**Question 2. The S.I. unit of G is ______.**

- m/s
- Nm
^{2}/kg^{2} - N
- Dyne

**Answer.** 2. Nm^{2}/kg^{2}

**Question 3. An object weighs 10 N when measured on the surface of earth. What should be its weight on moon?**

- 1.67 N
- 4.18 N
- 2.20 N
- 16.7 N

**Answer.** 1. 1.67 N

**Question 4. According to Newton, the force of attraction (F) between two particles is:**

- Inversely proportional to the product of their masses
- Directly proportional to the their masses
- Inversely proportional to the their masses
- Directly proportional to the product of their masses

**Answer.** 4. Directly proportional to the product of their masses

**Question 5. ______ between two bodies forms action reaction pair.**

- Kinetic energy
- Acceleration
- Gravitational force
- Potential energy

**Answer.** 3. Gravitational force

## Chapter 3 Gravitation Mass

**Question 1. The force with which the earth ______ an object is called force due to gravity on the object.**

- attracts
- repel
- forms
- moves

**Answer.** 1. attracts

**Question 2. The value of g is maximum**

- at equator of earth
- at poles of earth
- in a mine
- at a high hill

**Answer.** 2. at poles of earth

**Question 3. Acceleration due to gravity ______ with depth below the surface of the earth.**

- increases
- decreases
- doubles
- becomes half

**Answer.** 2. decreases

**Question 4. A ball is thrown vertically upwards and attains a maximum height of 100 m. It was thrown with a speed.**

- 9.8 m/s
- 44.3 m/s
- 19.6 m/s
- 98 m/s

**Answer.** 2. 44.3 m/s

**Question 5. The value of g is _______ on different planets and satellites**

- different
- same
- equivalent
- None of the above

**Answer.** 1. different

## Chapter 3 Gravitation Thrust and Pressure

**Question 1. Relative density has _________ unit.**

**Answer.** No

**Question 2. The relative density of water** **is**

- Zero
- One
- Two
- Can’t say

**Answer.** 2. One

**Question 3. If the relative density of an object is less than that of water, then it will**

- Rise
- Float
- Sink
- Can’t say

**Answer.** 2. Float

**Question 4. Archimedes’ principle is applicable to the objects in fluids. (True/False)**

**Answer.** True

## Chapter 3 Gravitation Practice Exercises

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

- have same velocities at any instant
- have different accelerations
- experience forces of same magnitude
- undergo a change in their inertia

**Answer.** 1. have same velocities at any instant

**Question 2. The value of acceleration due to gravity**

- is same on equator and poles
- is least on poles
- is least on equator
- increases from pole to equator

**Answer.** 3. is least on equator

**Question 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**

- F/4
- F/2
- F
- 2 F

**Answer.** 1. F/4

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

- will continue to move in the circular path
- will move along a straight line towards the centre of the circular path
- will move along a straight line tangential to the circular path
- will move along a straight line perpendicular to the circular path away from the boy

**Answer.** 3. will move along a straight line tangential to the circular path

**Question 5. An object is put one by one in three liquids having different densities. The object floats with 1/9 2/11 and 3/7 , and parts of their volumes outside the liquid surface in liquids of densities d _{1}, d_{2} and d_{3} respectively. Which of the following statement is correct?**

- d
_{1}> d_{2}> d_{3} - d
_{1}> d_{2}< d_{3} - d
_{1}< d_{2}> d_{3} - d
_{1}< d_{2}< d_{3}

**Answer.** 4. d_{1} < d_{2} < d_{3}

**Question 6. In the relation F = GMm/d ^{2}, the quantity G**

- depends on the value of g at the place of observation
- is used only when the earth is one of the two masses
- is greatest at the surface of the earth
- is universal constant of nature

**Answer.** 4. is universal constant of nature

**Question 7. Law of gravitation gives the gravitational force between**

- the earth and a point mass only
- the earth and Sun only
- any two bodies having some mass
- two charged bodies only

**Answer.** 3. any two bodies having some mass

**Question 8. The value of quantity G in the law of gravitation**

- depends on mass of earth only
- depends on radius of earth only
- depends on both mass and radius of earth
- is independent of mass and radius of the earth

**Answer.** 4. is independent of mass and radius of the earth

**Question 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**

- \(\frac{1}{4} \text { times }\)
- 4 times
- \(\frac{1}{2} \text { times }\)
- unchanged

**Answer.** 2. 4 times

**Question 10. The atmosphere is held to the earth by**

- gravity
- wind
- clouds
- earth’s magnetic field

**Answer.** 1. gravity

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

- gravitational potential
- acceleration due to gravity
- gravitational field
- universal gravitational constant

**Answer.** 4. universal gravitational constant

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

- zero
- infinite
- R times the weight at the surface of the earth
- 1/R2 times the weight at surface of the earth

**Answer.** 1. zero

**Question 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**

- 2 N
- 8 N
- 10 N
- 12 N

**Answer.** 1. 2 N

**Question 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**

- maximum when length and breadth form the base
- maximum when breadth and width form the base
- maximum when width and length form the base
- the same in all the above three cases

**Answer.** 2. maximum when breadth and width form the base

**Question 15. An apple falls from a tree because of gravitational attraction between the earth and apple. If F _{1} is the magnitude of force exerted by the earth on the apple and F_{2} is the magnitude of force exerted by apple on earth, then**

- F
_{1}is very much greater than F_{2} - F
_{2}is very much greater than F_{1} - F
_{1}is only a little greater than F_{2} - F
_{1}and F_{2}are equal

**Answer.** 4. F_{1} and F_{2} are equal