# Upthrust in Fluids, Archimedes’ Principle and Floatation Exe-5A Very Short Answer Physics Class-9 ICSE Selina Publishers

Upthrust in Fluids, Archimedes’ Principle and Floatation Exe-5A Upthrust and Archimedes Principle Very Short Answer Type for Class-9 ICSE Concise Physics. There is the solutions of Very short Answer type Questions of your latest textbook which is applicable in 2023-24 academic sessionVisit official Website CISCE for detail information about ICSE Board Class-9.

## Upthrust in Fluids, Archimedes’ Principle and Floatation Exe-5A Very Short Answer

(ICSE Class – 9 Physics Concise Selina Publishers)

 Board ICSE Class 9 Subject Physics Writer / Publication Concise selina Publishers Chapter-5 Upthrust in Fluids, Archimedes’ Principle and Floatation Exe – 5A Upthrust and Archimedes Principle Topics Solution of Exe-5(A) Very Short Answer Type Academic Session 2023-2024

### Exe-5A Upthrust and Archimedes Principle Very Short Answer Type

Ch-5 Upthrust in Fluids, Archimedes’ Principle and Floatation Physics Class-9 ICSE Concise

Page 121

#### Question 1. In what direction and at what point does the buoyant force on a body due to a liquid act?

Buoyant force on a body due to a liquid acts upwards at the centre of buoyancy.

#### Question 2. Define upthrust and state its S.I. unit.

The upward force exerted on a body by the fluid in which it is submerged is called the upthrust. Its S.I. unit is ‘newton’.

#### Question 3. Why is a force needed to keep a block of wood inside water?

Upthrust due to water on block when fully submerged is more than its weight. Density of water is more than the density of cork; hence, upthrust due to water on the block of cork when fully submerged in water is more than its weight.

#### Question 4. 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.

F2  F1; Sea water is denser than river water; therefore, the upthrust due to sea water will be greater than that due to river water at the same level. This shall make the body to appear lighter in the sea water.

Exe-5A Upthrust and Archimedes Principle Very Short Answer Type

### Ch-5 Upthrust in Fluids, Archimedes’ Principle and Floatation Physics Class-9 ICSE Concise

Page 122

#### Question 5. A body of volume V and density ρ is kept completely immersed in a liquid of density ρL . If g is the acceleration due to gravity, then 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.

(i) Weight of the body =  Vρg

(ii) Upthrust on the body =  VρLg

(iii) Apparent weight of the body in liquid = V(ρ – ρL)g

(iv) Loss in weight of the body =  VρLg

#### Question 6. Complete the following sentences:

(a) Two balls, one of iron and the other of aluminium 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 2 m 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.

(a) Both have equal volumes. (b) Bounce back to the surface.

(c) More than

#### Question 7. A sphere of iron and another sphere of wood of the same radius are held under water. Compare the upthrust on the two spheres.

Hint: Both have equal volume inside the water.

Since the spheres have the same radius, both will have an equal volume inside water, and hence, the upthrust acted by water on both the spheres will be the same.

Hence, the required ratio of upthrust acting on two spheres is 1:1.

(Upthrust in Fluids Exe-5A Very Short ICSE)

#### Question 8. A body of density ρ is immersed in a liquid of density. State the condition when the body will (i) float and (ii) sink in the liquid.

(i) The body will float if ρ <  or = ρL

(ii) The body will sink if  ρ  > ρL

#### Question 9. State the Archimedes’ principle.

Archimedes’ principle states that when a body is immersed partially or completely in a liquid, it experiences an upthrust, which is equal to the weight of liquid displaced by it.

—  : End of Upthrust in Fluids, Archimedes’ Principle and Floatation Exe-5A Very Short Answer Type  Solutions :–

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