(English Medium) ICSE Class 9 - CISCE Question Bank Solutions for Physics

A piece of wood if left under water comes to the surface. Explain the reason. 

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

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

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

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. 

A small block of wood is 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. 

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

Complete the following sentence :

Two balls, one of iron and the other of aluminium experience the same upthrust when dipped completely in water if _____________ .

Complete the following sentence :

A piece of wood is held under water. The upthrust on it will be ___________  the weight of the wood piece. 

Prove that the loss in weight of a body when immersed wholly or partially in a liquid is equal to the buoyant force (or upthrust) and this loss is because of the difference in pressure exerted by liquid on the upper and lower surfaces of the submerged part of body. 

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

A body will experience minimum upthrust when it is completely immersed in : 

The S.I. unit of upthrust is : 

A body weighs 450 gf in air and 310 gf when completely immersed in water. Find 

(i) The volume of the body,

(ii) The loss in weight of the body, and

(iii) The upthrust on the body.

State the assumption made in part (i). 

You are provided with a hollow iron ball A of volume 15 cm³ and mass 12 g and a solid iron ball B of mass 12 g. Both are placed on the surface of water contained in a large tub.

1. Find upthrust on each ball.
2. Which ball will sink? Give a reason for your answer (Density of iron = 8.0 g cm^-3) 

Two spheres A and B, each of volume 100 cm³ is placed on water (density = 1.0 g cm⁻³). The sphere A is made of wood of density 0.3 g cm⁻³ and sphere B is made of iron of density 8.9 g cm⁻³.

1. Find:
   1. The weight of each sphere, and
   2. The upthrust on each sphere.
2. Which sphere will float? Give reason.

The mass of a block made of certain material is 13.5 kg and its volume is 15 × 10^-3 m³.

(a) Calculate upthrust on the block if it is held fully immersed in water.

(b) Will the block float or sink in water when released? Give a reason for your answer.

(c) What will be the upthrust on block while floating?

Take density of water = 1000 kg m^-3. 

A block of wood is floating on water with its dimensions 50 cm x 50 cm x 50 cm inside water. Calculate the buoyant force acting on the block. Take g = 9.8 N kg^-1. 

A body of mass 3.5 kg displaces 1000 cm³ of water when fully immersed inside it. Calculate:

1. the volume of body,
2. the upthrust on body and
3. the apparent weight of body in water. 

Complete the following sentence.

Mass = .................... × density