Q1 What do you understand by the term upthrust of a fluid? Describe an experiment to show its existence.

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Q2 In what direction and at what point does the buoyant force on a body due to a liquid, act?

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Q3 What is meant by the term buoyancy?

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Q4 Define upthrust and state its S.I. unit.

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Q5 What is the cause of upthrust? At which point it can be considered to act?

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Q6 Why is a force needed to keep a block of wood inside water?

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Q7 Why is a force needed to keep a block of wood inside water?

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Q8 Describe an experiment to show that a body immersed in a liquid appears lighter than it really is

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Q9 Will a body weigh more in air or in vaccum when weighed with a spring balance? Give a reason for your answer.

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Q10 A metal solid cylinder tied to a thread is hanging from the hook of a spring balance. The cylinder is gradually immersed into water contained in a jar. What changes do you expect in the readings of spring balance? Explain your answer.

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Q11 A body dipped into a liquid experiences an upthrust. State two factors on which upthrust on the body depends.

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Q12 How is the upthrust related to the volume of the body submerged in a liquid?

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Q13 A bunch of feathers and a stone of the same mass are released simultaneously in air. Which will fall faster and why? How will your observation be different if they are released simultaneously in vaccum?

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Q14 A body experiences an upthrust F1 in river water and F2 in sea water when dipped up to the same level. Which is more F1 or F2? Give reason.

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Q15 A small block of wood is held completely immersed in (i) water, (ii) glycerine and then released. In each case, what do you observe? Explain the difference in your observation in the two cases

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Q16 A body of volume V and density ρ is kept completely immersed in a liquid of density ρL . If g id the acceleration due to gravity, write expressions for the following:
(i) The weight of the body
(ii) The upthrust on the body
(iii) The apparent weight of the body in liquid
(iv) The loss in weight of the body.

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Q17 A body held completely immersed inside a liquid experiences two forces: (i) F1, the force due to gravity and (ii) F2, the buoyant force. Draw a diagram showing the direction of these forces acting on the body and state the conditions when the body will float or sink.

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Q18 Complete the following sentences:
(a) Two balls, one of iron and the other of aluminum experience the same upthrust when dipped completely in water if ________________
(b) An empty tin container with its mouth closed has an average density equal to that of a liquid. The container is taken 2m below the surface of that liquid and is left there. Then the container will ___________
(c) A piece of wood is held under water. The upthrust on it will be ___________ the weight of the wood piece.

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Q19 A sphere of iron and another of wood of the same radius are held under water. Compare the upthrust on the two spheres.

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Q20 A sphere of iron and another of wood of the same radius are held under water. Compare the upthrust on the two spheres.

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Q21 A sphere of iron and another of wood, both of same radius are placed on the surface of water. State which of the two will sink? Give reason to your answer.

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Q22 How does the density of material of a body determine whether it will float or sink in water?

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Q23 A body of density ρ is immersed in a liquid of density ρL. State condition when the body will (i) float, (ii) sink, in liquid.

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Q24 It is easier to lift a heavy stone under water than in air. Explain.

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Q25 State Archimedes’ principle.

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Q26 Describe an experiment to verify Archimedes’ principle.

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Multiple Choice type Questions :

Q1 A body will experience minimum upthrust when it is completely immersed in:
(a) Turpentine
(b) Water
(c) Glycerine
(d) Mercury

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Q2 The S.I. unit of upthrust is:
(a) Pa
(b) N
(c) kg
(d) kg m-3

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Q3 A body of density ρ sinks in a liquid of density ρL. The densities ρ and ρL are related as:
(a) ρ = ρL
(b) ρ < ρL
(c) ρ > ρL
(d) nothing can be said

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