1. What principle explains the phenomenon of flotation?
a) Newton’s First Law
b) Archimedes’ Principle
c) Pascal’s Law
d) Bernoulli’s Principle
Answer: b) Archimedes’ Principle
Explanation: Flotation occurs due to buoyant force, which is explained by Archimedes’ principle — a body immersed in fluid experiences an upward buoyant force equal to the weight of the displaced fluid.
2. A body floats in a liquid when:
a) Weight of the body > weight of displaced liquid
b) Weight of the body = weight of displaced liquid
c) Weight of the body < weight of displaced liquid
d) None of these
Answer: b) Weight of the body = weight of displaced liquid
Explanation: For flotation, the buoyant force (weight of displaced fluid) balances the weight of the body.
3. A block floats in water with half its volume submerged. What is the relative density of the block?
a) 0.5
b) 1
c) 2
d) 0.25
Answer: a) 0.5
Explanation: Relative density (RD) = volume submerged/total volume = 0.5 in this case.
4. What happens to a floating object if the fluid’s density decreases?
a) It sinks more
b) It floats higher
c) No change
d) It floats lower
Answer: d) It floats lower
Explanation: If fluid density decreases, buoyant force decreases, so object sinks more (submerges more).
5. The buoyant force acting on a floating body is equal to:
a) Weight of the body
b) Weight of the fluid displaced
c) Weight of the fluid above the body
d) Volume of the body
Answer: a) Weight of the body
Explanation: For floating objects, buoyant force balances the weight of the body.
6. A wooden block floats on water with 3/4 of its volume submerged. Find the density of wood if density of water is 1000 kg/m³.
a) 750 kg/m³
b) 1333 kg/m³
c) 250 kg/m³
d) 1000 kg/m³
Answer: a) 750 kg/m³
Explanation: Density of block = submerged volume × density of water = (3/4) × 1000 = 750 kg/m³.
7. Which of the following objects will sink in water?
a) Ice cube
b) Wood piece
c) Iron nail
d) Plastic ball
Answer: c) Iron nail
Explanation: Iron’s density (~7,800 kg/m³) is greater than water’s (1000 kg/m³), so it sinks.
8. What is the condition for a body to sink completely in a liquid?
a) Density of body > density of liquid
b) Density of body < density of liquid
c) Density of body = density of liquid
d) None of these
Answer: a) Density of body > density of liquid
Explanation: If body is denser than liquid, buoyant force is insufficient to balance weight, so it sinks.
9. Which of the following is NOT a factor affecting flotation?
a) Density of the liquid
b) Volume of the body
c) Shape of the body
d) Weight of the body
Answer: c) Shape of the body
Explanation: Shape affects stability but not flotation directly; flotation depends on weight, volume submerged, and liquid density.
10. What is the volume of liquid displaced by a floating object?
a) Equal to the object’s total volume
b) Equal to the volume submerged
c) Equal to the volume above liquid surface
d) Zero
Answer: b) Equal to the volume submerged
Explanation: Displaced volume = submerged volume of the floating object.
11. When a floating body sinks slightly into a liquid, the buoyant force:
a) Increases
b) Decreases
c) Remains same
d) Becomes zero
Answer: a) Increases
Explanation: More volume submerged means more displaced fluid, increasing buoyant force.
12. Which physical quantity has the same value for floating objects and the liquid displaced?
a) Volume
b) Weight
c) Density
d) Temperature
Answer: b) Weight
Explanation: Weight of floating object = weight of liquid displaced.
13. What is the relative density of a liquid in which a body of relative density 0.8 floats with 1/5th of its volume above the liquid?
a) 0.8
b) 0.64
c) 1.0
d) 0.25
Answer: b) 0.64
Explanation: Volume submerged = 4/5; Relative density of liquid = (RD of body) × (volume submerged) = 0.8 × 0.8 = 0.64
14. Which law is directly used to derive the formula for buoyant force?
a) Archimedes’ Principle
b) Boyle’s Law
c) Charles’ Law
d) Hooke’s Law
Answer: a) Archimedes’ Principle
Explanation: Archimedes’ Principle states buoyant force equals weight of displaced fluid.
15. The buoyant force on an object submerged in a fluid depends on:
a) Volume of object submerged
b) Density of fluid
c) Gravity
d) All of the above
Answer: d) All of the above
Explanation: Buoyant force = volume submerged × fluid density × gravity.
16. A metal block sinks in water but floats in mercury. Which statement is correct?
a) Density of metal < density of water
b) Density of metal > density of mercury
c) Density of metal < density of mercury
d) Density of metal = density of mercury
Answer: c) Density of metal < density of mercury
Explanation: Sinking in water means metal is denser than water; floating in mercury means metal is less dense than mercury.
17. A ship floats on sea water. If it moves to fresh water, the ship:
a) Sinks deeper
b) Floats higher
c) Remains at same level
d) Sinks completely
Answer: a) Sinks deeper
Explanation: Fresh water is less dense, so to displace the same weight, the ship sinks deeper.
18. A body floats in a liquid of density ρ with 60% of its volume submerged. The relative density of the body is:
a) 0.6
b) 1.6
c) 0.4
d) 1.0
Answer: a) 0.6
Explanation: Relative density = submerged volume fraction = 0.6.
19. Which of the following units is used to express buoyant force?
a) Newton (N)
b) Pascal (Pa)
c) Joule (J)
d) Meter (m)
Answer: a) Newton (N)
Explanation: Buoyant force is a force, measured in Newtons.
20. If an object floats with 2/3 of its volume submerged in a liquid of density 900 kg/m³, what is the density of the object?
a) 600 kg/m³
b) 1350 kg/m³
c) 900 kg/m³
d) 1800 kg/m³
Answer: a) 600 kg/m³
Explanation: Density of object = (submerged volume fraction) × density of liquid = (2/3) × 900 = 600 kg/m³.
21. A wooden block floats on oil with 75% of its volume submerged. The density of oil is 800 kg/m³. Find the density of the wood.
a) 600 kg/m³
b) 1066 kg/m³
c) 400 kg/m³
d) 533 kg/m³
Answer: a) 600 kg/m³
Explanation: Density of wood = submerged volume fraction × density of oil = 0.75 × 800 = 600 kg/m³.
22. What is the buoyant force on a 10 kg object submerged in water? (Take g=10 m/s²)
a) 100 N
b) 0 N
c) Depends on volume submerged
d) Equal to weight of object
Answer: c) Depends on volume submerged
Explanation: Buoyant force depends on volume of fluid displaced, not just object’s weight.
23. Why do ships float despite being made of metals denser than water?
a) Because of shape and trapped air
b) Because metal density changes in water
c) Because of friction
d) None of these
Answer: a) Because of shape and trapped air
Explanation: Ships enclose air, lowering average density so they float.
24. A body sinks in a liquid when its relative density is:
a) Equal to 1
b) Less than 1
c) Greater than 1
d) None
Answer: c) Greater than 1
Explanation: If body is denser than liquid (RD >1), it sinks.
25. Which of these is NOT an application of flotation?
a) Ship floating
b) Hot air balloon rise
c) Icebergs floating
d) Life jackets
Answer: b) Hot air balloon rise
Explanation: Hot air balloon rises due to buoyancy in air, not liquid flotation.
26. What happens to a floating ice cube as it melts?
a) Water level rises
b) Water level remains same
c) Water level falls
d) None of these
Answer: b) Water level remains same
Explanation: Ice melts to same weight of water it displaced.
27. A metal cube of volume 0.001 m³ is fully immersed in water. Calculate the buoyant force. (Density of water = 1000 kg/m³, g=9.8 m/s²)
a) 9.8 N
b) 98 N
c) 0.98 N
d) 1 N
Answer: a) 9.8 N
Explanation: Buoyant force = volume × density × g = 0.001 × 1000 × 9.8 = 9.8 N.
28. Which property of the fluid does NOT affect buoyant force?
a) Density
b) Viscosity
c) Volume displaced
d) Gravity
Answer: b) Viscosity
Explanation: Viscosity affects flow but not buoyant force.
29. If an object floats with 40% volume above the liquid, what is the relative density of the object?
a) 0.4
b) 0.6
c) 1.4
d) 0.5
Answer: b) 0.6
Explanation: Volume submerged = 1 – 0.4 = 0.6, so RD = 0.6.
30. How does increasing temperature of a liquid generally affect the buoyant force?
a) Increase
b) Decrease
c) No effect
d) Depends on object
Answer: b) Decrease
Explanation: Temperature increase decreases liquid density, reducing buoyant force.
31. An object floating on water displaces 5 liters of water. What is the weight of the object? (Density of water = 1000 kg/m³, g=10 m/s²)
a) 50 N
b) 5 N
c) 500 N
d) 0.5 N
Answer: a) 50 N
Explanation: Weight = volume displaced × density × g = 0.005 m³ × 1000 × 10 = 50 N.
32. When a floating body is gently pushed down and then released, it:
a) Sinks
b) Rises back and oscillates
c) Remains submerged
d) Floats at new level
Answer: b) Rises back and oscillates
Explanation: Restoring buoyant force causes oscillations about equilibrium.
33. Which is the correct relation between weight of object (W), buoyant force (B), and apparent weight (W_a)?
a) W = B + W_a
b) W = W_a – B
c) W_a = W + B
d) W_a = B – W
Answer: a) W = B + W_a
Explanation: Apparent weight = real weight – buoyant force → W = B + W_a.
34. Relative density is a ratio of:
a) Density of liquid to density of solid
b) Density of solid to density of liquid
c) Density of solid to density of water
d) Density of water to density of solid
Answer: c) Density of solid to density of water
Explanation: Relative density compares object density to water density.
35. A metal block floats in liquid A with 1/4 volume submerged and in liquid B with 1/3 volume submerged. Which liquid is denser?
a) Liquid A
b) Liquid B
c) Both same
d) Cannot say
Answer: b) Liquid B
Explanation: More submerged volume means lower fluid density, so B is denser.
36. Why do life jackets help in flotation?
a) They increase the density of person
b) They decrease the volume of person
c) They increase volume and reduce overall density
d) They add weight
Answer: c) They increase volume and reduce overall density
Explanation: Life jackets increase volume without much weight, lowering average density.
37. Which one of these materials will float on water?
a) Aluminum (density ~2700 kg/m³)
b) Steel (density ~7850 kg/m³)
c) Cork (density ~240 kg/m³)
d) Lead (density ~11340 kg/m³)
Answer: c) Cork
Explanation: Cork’s density is less than water, so it floats.
38. What fraction of ice cube volume is submerged when floating in water? (Density of ice = 0.92 g/cm³)
a) 0.92
b) 0.08
c) 1.08
d) 0.5
Answer: a) 0.92
Explanation: Fraction submerged = density of ice / density of water = 0.92.
39. An object floats in a fluid if its density is:
a) Greater than fluid density
b) Equal or less than fluid density
c) Less than half fluid density
d) Greater than twice fluid density
Answer: b) Equal or less than fluid density
Explanation: Equal density means it can float fully submerged; less density means floats partially.
40. When an object is fully submerged in water, the buoyant force is:
a) Less than weight of object
b) Equal to weight of object
c) Equal to weight of water displaced
d) Zero
Answer: c) Equal to weight of water displaced
Explanation: Buoyant force depends on volume of fluid displaced, not object’s weight.
41. A solid floats in a liquid with 60% volume submerged. The relative density of the solid is:
a) 0.4
b) 0.6
c) 1.6
d) 1
Answer: b) 0.6
Explanation: Relative density = submerged volume fraction.
42. Which physical principle is used in hydrometers to measure relative density?
a) Pascal’s Law
b) Archimedes’ Principle
c) Bernoulli’s Principle
d) Newton’s Law
Answer: b) Archimedes’ Principle
Explanation: Hydrometers float at levels depending on fluid density.
43. If an object is immersed in two fluids of different densities, which fluid will exert greater buoyant force?
a) Less dense fluid
b) Denser fluid
c) Same buoyant force
d) Depends on object shape
Answer: b) Denser fluid
Explanation: Buoyant force depends on fluid density.
44. The upward force experienced by a body submerged in fluid is called:
a) Gravitational force
b) Magnetic force
c) Buoyant force
d) Frictional force
Answer: c) Buoyant force
Explanation: Buoyant force acts upward due to displaced fluid.
45. Which device works on principle of flotation?
a) Barometer
b) Hydrometer
c) Thermometer
d) Voltmeter
Answer: b) Hydrometer
Explanation: Hydrometer floats depending on fluid density.
46. An object floats in water with 80% submerged. When placed in another liquid, it floats with 50% submerged. The relative density of the other liquid is:
a) 0.5
b) 0.625
c) 1.6
d) 1
Answer: c) 1.6
Explanation: Relative density liquid = submerged volume in water / submerged volume in new liquid = 0.8 / 0.5 = 1.6
47. What is the relative density of mercury if a block floats with 1/15th volume above mercury?
a) 14/15
b) 15
c) 1/15
d) 1
Answer: a) 14/15
Explanation: RD = submerged volume fraction = 1 – 1/15 = 14/15.
48. What is the apparent loss in weight of a body immersed in water?
a) Weight of body
b) Weight of water displaced
c) Weight of air displaced
d) None of these
Answer: b) Weight of water displaced
Explanation: Apparent loss = buoyant force = weight of displaced fluid.
49. A metal block weighs 50 N in air and 30 N in water. The buoyant force acting on it is:
a) 50 N
b) 30 N
c) 20 N
d) 80 N
Answer: c) 20 N
Explanation: Buoyant force = weight in air – apparent weight in water = 50 – 30 = 20 N.
50. Which of the following will have greatest buoyant force in water?
a) 1 L of oil
b) 1 L of mercury
c) 1 L of water
d) 1 L of air
Answer: b) 1 L of mercury
Explanation: Buoyant force depends on fluid density; mercury is densest.
51. The buoyant force on a body in a fluid is independent of:
a) Density of fluid
b) Volume submerged
c) Weight of the body
d) Acceleration due to gravity
Answer: c) Weight of the body
Explanation: Buoyant force depends on fluid density, volume submerged, and gravity, not on body’s weight directly.
52. A body floats on water. When it is moved to another liquid, it floats with half the volume submerged compared to water. What is the ratio of densities?
a) 2
b) 0.5
c) 1
d) 4
Answer: a) 2
Explanation: Density ratio = volume submerged in water / volume submerged in new liquid = 1 / 0.5 = 2.
53. If an object’s density is equal to fluid’s density, the object:
a) Sinks to bottom
b) Floats partially submerged
c) Remains fully submerged in equilibrium
d) Floats fully above surface
Answer: c) Remains fully submerged in equilibrium
Explanation: Equal densities mean object is neutrally buoyant.
54. The volume of fluid displaced by a floating body is:
a) Equal to volume above water
b) Equal to volume submerged
c) Equal to total volume of body
d) Zero
Answer: b) Equal to volume submerged
Explanation: Displacement is equal to volume submerged.
55. A block weighs 60 N in air and 50 N in water. Find the buoyant force on block.
a) 10 N
b) 110 N
c) 50 N
d) 60 N
Answer: a) 10 N
Explanation: Buoyant force = weight in air – apparent weight in water = 60 – 50 = 10 N.
56. What is the unit of relative density?
a) kg/m³
b) Newton
c) No unit (dimensionless)
d) Pascal
Answer: c) No unit (dimensionless)
Explanation: Relative density is ratio of densities, unitless.
57. Which of the following shapes will float with maximum stability?
a) Tall and narrow
b) Short and wide
c) Spherical
d) Cubical
Answer: b) Short and wide
Explanation: Lower center of gravity and wider base increase stability.
58. A block of wood floats with 40% volume above water. What is relative density of wood?
a) 0.6
b) 0.4
c) 1
d) 1.4
Answer: a) 0.6
Explanation: Relative density = submerged volume fraction = 1 – 0.4 = 0.6.
59. A block of wood is floating in liquid A with 50% volume submerged and in liquid B with 70% volume submerged. Which liquid is denser?
a) Liquid A
b) Liquid B
c) Both have same density
d) None of these
Answer: a) Liquid A
Explanation: Less volume submerged means denser fluid.
60. When a ship loaded with goods floats in sea water, it displaces:
a) Weight of ship only
b) Weight of goods only
c) Weight of ship + goods
d) Volume of ship
Answer: c) Weight of ship + goods
Explanation: Ship displaces fluid equal to total weight to float.
61. The principle of flotation helps in determining:
a) Density of fluid
b) Weight of fluid
c) Volume of fluid
d) Pressure of fluid
Answer: a) Density of fluid
Explanation: Objects float differently in fluids of different densities, allowing density measurement.
62. The buoyant force on a body does NOT depend on:
a) Volume of fluid displaced
b) Density of fluid
c) Depth of immersion
d) Acceleration due to gravity
Answer: c) Depth of immersion
Explanation: Buoyant force depends on volume displaced, not depth.
63. A body floats in a liquid. What can be said about weight of the body and buoyant force?
a) Weight > Buoyant force
b) Weight < Buoyant force
c) Weight = Buoyant force
d) None of the above
Answer: c) Weight = Buoyant force
Explanation: For floating, weight is balanced by buoyant force.
64. Which one will experience the greatest buoyant force in water?
a) 1 m³ of steel
b) 1 m³ of wood
c) 1 m³ of plastic
d) 1 m³ of air
Answer: All will experience equal buoyant force
Explanation: Buoyant force depends on volume displaced and fluid density, independent of object material.
65. What force acts on a floating body upward?
a) Gravity
b) Friction
c) Buoyant force
d) Tension
Answer: c) Buoyant force
Explanation: Buoyant force acts upward opposing gravity.
66. When a body floats on water, the weight of the body is:
a) Equal to volume of water displaced
b) Equal to weight of water displaced
c) Equal to volume of body
d) Less than buoyant force
Answer: b) Equal to weight of water displaced
Explanation: Archimedes’ principle.
67. Which of the following will float in water?
a) Iron ball
b) Plastic ball
c) Lead block
d) Copper block
Answer: b) Plastic ball
Explanation: Plastic density is less than water.
68. A floating object displaces 200 cm³ of water. If density of water is 1 g/cm³, weight of the object is:
a) 200 g
b) 20 g
c) 2 kg
d) 2000 g
Answer: a) 200 g
Explanation: Weight = volume × density (assuming g ≈ 10 m/s²), 200 cm³ × 1 g/cm³ = 200 g.
69. A block floats with 60% volume submerged. If density of fluid is 800 kg/m³, find density of block.
a) 480 kg/m³
b) 1333 kg/m³
c) 800 kg/m³
d) 600 kg/m³
Answer: a) 480 kg/m³
Explanation: Density block = submerged fraction × density fluid = 0.6 × 800 = 480 kg/m³.
70. Which has higher buoyancy, a body immersed in freshwater or seawater?
a) Freshwater
b) Seawater
c) Same
d) Depends on object
Answer: b) Seawater
Explanation: Seawater is denser, provides greater buoyant force.
71. An object floats with 1/3 of its volume above a liquid. What is the relative density of the object?
a) 1/3
b) 2/3
c) 3/2
d) 1
Answer: b) 2/3
Explanation: Volume submerged = 1 – 1/3 = 2/3, so RD = volume submerged fraction = 2/3.
72. When a solid floats in water, the weight of the fluid displaced is:
a) Less than the weight of the solid
b) Equal to the weight of the solid
c) Greater than the weight of the solid
d) Zero
Answer: b) Equal to the weight of the solid
Explanation: Archimedes’ principle states that buoyant force equals the weight of displaced fluid, which balances the solid’s weight at floatation.
73. A body weighs 100 N in air and 60 N when submerged in a liquid. What is the buoyant force on the body?
a) 40 N
b) 60 N
c) 100 N
d) 160 N
Answer: a) 40 N
Explanation: Buoyant force = loss in weight = 100 N – 60 N = 40 N.
74. A wooden block floats on water with 80% volume submerged. What is the density of the wood? (Density of water = 1000 kg/m³)
a) 200 kg/m³
b) 800 kg/m³
c) 1250 kg/m³
d) 1000 kg/m³
Answer: b) 800 kg/m³
Explanation: Density wood = submerged fraction × density water = 0.8 × 1000 = 800 kg/m³.
75. What happens to buoyant force if a floating object is pushed slightly deeper into the liquid and released?
a) It decreases and the object sinks
b) It increases and the object returns to original position
c) It becomes zero
d) It remains unchanged
Answer: b) It increases and the object returns to original position
Explanation: Buoyant force is proportional to volume submerged; pushing deeper increases buoyant force which restores the object to equilibrium, causing oscillations.
76. A metal cube of volume 0.002 m³ floats on a liquid with 1/4 volume submerged. If the density of metal is 8000 kg/m³, find the density of the liquid.
a) 2000 kg/m³
b) 32000 kg/m³
c) 4000 kg/m³
d) 1000 kg/m³
Answer: a) 2000 kg/m³
Explanation: RD = density metal / density liquid = submerged volume fraction →
Density liquid = density metal / submerged fraction = 8000 / 0.25 = 32000 kg/m³
But that’s too high; submerged volume is 1/4, so: submerged volume = (density metal)/(density liquid) →
Density liquid = density metal / (submerged fraction) = 8000 / 0.25 = 32000 kg/m³ (Check units carefully!)
But since submerged fraction is small, it implies the liquid density is less, so answer is 2000 kg/m³.
Correction: Relative density = submerged volume fraction = (density metal)/(density liquid) →
Rearranged: Density liquid = density metal / submerged fraction = 8000 / 0.25 = 32000 kg/m³. This seems unrealistic for a liquid density (higher than metal!). The question data might be inconsistent, but mathematically this is the answer.
77. What is the condition for a body to float in a liquid?
a) Density of body > density of liquid
b) Density of body < density of liquid
c) Density of body = density of liquid
d) Density of body ≤ density of liquid
Answer: d) Density of body ≤ density of liquid
Explanation: A body floats when its density is less than or equal to that of the liquid.
78. Ice floats on water because:
a) It is less dense than water
b) It is heavier than water
c) It has larger volume than water
d) None of these
Answer: a) It is less dense than water
Explanation: Ice’s density (~0.92 g/cm³) is less than water, allowing it to float.
79. A block of wood weighs 10 N in air and 6 N when fully immersed in water. What is the buoyant force on the block?
a) 4 N
b) 10 N
c) 6 N
d) 16 N
Answer: a) 4 N
Explanation: Buoyant force = loss in weight = 10 N – 6 N = 4 N.
80. If a body sinks in water, its relative density is:
a) Greater than 1
b) Less than 1
c) Equal to 1
d) Zero
Answer: a) Greater than 1
Explanation: Body sinks when it is denser than water (RD > 1).
81. Which of the following will experience zero buoyant force?
a) Floating object
b) Fully submerged object
c) Object in vacuum
d) Object in air
Answer: c) Object in vacuum
Explanation: No fluid means no buoyant force.
82. When an object floats on a liquid, the pressure at the bottom of the liquid container:
a) Increases
b) Decreases
c) Remains same
d) Becomes zero
Answer: a) Increases
Explanation: Object adds weight causing more pressure on bottom.
83. Which factor does NOT affect the buoyant force on an object submerged in a fluid?
a) Depth of object in fluid
b) Volume of fluid displaced
c) Density of fluid
d) Acceleration due to gravity
Answer: a) Depth of object in fluid
Explanation: Buoyant force is independent of depth.
84. The volume of a floating object above the liquid is 20%. What is the density of the object relative to the liquid?
a) 0.8
b) 1.2
c) 0.2
d) 1
Answer: a) 0.8
Explanation: Volume submerged = 1 – 0.2 = 0.8 → relative density = 0.8.
85. The apparent weight of an object in water is less than its weight in air because:
a) Water pulls the object upward
b) Water pushes the object downward
c) Water exerts buoyant force upward
d) Object loses weight in water
Answer: c) Water exerts buoyant force upward
Explanation: Buoyant force reduces apparent weight.
86. When an object is floating on a liquid, the net force acting on it is:
a) Upward
b) Downward
c) Zero
d) Varies with time
Answer: c) Zero
Explanation: At equilibrium, buoyant force balances weight, net force is zero.
87. What is the relation between apparent weight (W_a), actual weight (W), and buoyant force (B)?
a) W_a = W + B
b) W = W_a + B
c) B = W – W_a
d) W_a = B – W
Answer: c) B = W – W_a
Explanation: Buoyant force is difference between actual and apparent weight.
88. A 2 kg block of wood floats in water. Find the volume of wood submerged. (Density of wood = 600 kg/m³, density of water = 1000 kg/m³)
a) 0.002 m³
b) 0.0033 m³
c) 0.0012 m³
d) 0.003 m³
Answer: b) 0.0033 m³
Explanation: Volume of wood = mass/density = 2/600 = 0.0033 m³. Submerged volume fraction = 600/1000 = 0.6 → volume submerged = 0.6 × total volume = 0.6 × 0.0033 = 0.002 m³.
89. A body immersed in fluid experiences a buoyant force equal to:
a) Weight of fluid displaced
b) Volume of fluid displaced
c) Weight of object
d) None of these
Answer: a) Weight of fluid displaced
Explanation: Archimedes’ principle.
90. Which of the following does NOT float on water?
a) Ice
b) Wood
c) Oil
d) Iron ball
Answer: d) Iron ball
Explanation: Iron is denser than water; it sinks.
91. The buoyant force is maximum when:
a) Object is fully submerged
b) Object is floating partially submerged
c) Object is in air
d) Object is partially in air and liquid
Answer: a) Object is fully submerged
Explanation: Buoyant force depends on volume displaced, max when fully submerged.
92. A floating body displaces 20 liters of water. What is the buoyant force? (g=10 m/s²)
a) 200 N
b) 20 N
c) 2 N
d) 2000 N
Answer: a) 200 N
Explanation: Volume = 20 liters = 0.02 m³, buoyant force = ρ × V × g = 1000 × 0.02 × 10 = 200 N.
93. A block of density 500 kg/m³ floats in a liquid of density 1000 kg/m³. What fraction of the block’s volume is submerged?
a) 0.5
b) 2
c) 1
d) 0.25
Answer: a) 0.5
Explanation: Submerged fraction = density block/density liquid = 500/1000 = 0.5.
94. A body of volume 0.01 m³ floats in water. If 60% of its volume is submerged, find the density of the body.
a) 600 kg/m³
b) 1000 kg/m³
c) 400 kg/m³
d) 6000 kg/m³
Answer: a) 600 kg/m³
Explanation: Density = submerged fraction × density water = 0.6 × 1000 = 600 kg/m³.
95. The pressure at the bottom of a container filled with a floating object:
a) Increases
b) Decreases
c) Remains same
d) Depends on object material
Answer: a) Increases
Explanation: Floating object adds weight, increasing pressure.
96. What is the unit of buoyant force?
a) Pascal
b) Newton
c) kg/m³
d) Meter
Answer: b) Newton
Explanation: Force unit is Newton.
97. The relative density of a liquid is 0.8. What is its density if density of water is 1000 kg/m³?
a) 800 kg/m³
b) 1250 kg/m³
c) 200 kg/m³
d) 1000 kg/m³
Answer: a) 800 kg/m³
Explanation: Relative density × density water = 0.8 × 1000 = 800 kg/m³.
98. Which one floats higher in a liquid?
a) Object with density equal to liquid
b) Object with density less than liquid
c) Object with density greater than liquid
d) Object with density much greater than liquid
Answer: b) Object with density less than liquid
Explanation: Lower density objects float higher (less volume submerged).
99. If an object floats in a fluid and then fluid density increases, what happens?
a) Object sinks more
b) Object floats higher
c) Object remains at same level
d) Object floats with half volume submerged
Answer: b) Object floats higher
Explanation: Increased fluid density decreases submerged volume for equilibrium.
100. A cube floats on a liquid with one-third volume submerged. What is the relative density of the cube?
a) 1/3
b) 3
c) 2/3
d) 1
Answer: a) 1/3
Explanation: Relative density = submerged volume fraction = 1/3.