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

(i) The diameter of neck and bottom of a bottle are 2 cm and 10 cm, respectively. The bottle is completely filled with oil. If the cork in the neck is pressed in with a force of 1.2 kgf, what force is exerted on the bottom of the bottle?

(ii) Name the law/principle you have used to find the force in part (a).

Two cylindrical vessels fitted with pistons A and B of area of cross-section 8 cm² and 320 cm² respectively are joined at their bottom by a tube and they are completely filled with water. When a mass of 4 kg is placed on piston A, Find:

1. the pressure on piston A,
2. the pressure on piston B, and
3. the thrust on piston B.

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

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

What is meant by the term buoyancy? 

Define upthrust and state its S.I. unit. 

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

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

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 :