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

**Upthrust in Fluids, Archimedes’ Principle and Floatation Exe-5A Numericals 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) Numericals Answer Type |

Academic Session | 2023-2024 |

**Exe-5A Upthrust and Archimedes Principle Numericals Answer Type**

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

**Page 122**

**Question 1. **A body of volume 100 cm^{3} weighs 5 kgf in air. It is completely immersed in a liquid of density 1.8 x 10^{3} kg m^{-3}. Find:

(i) The upthrust due to liquid and

(ii) The weight of the body in liquid.

**Answer:**

weight of the body in air = W = 5 kgf

Volume of Body = V = 100³ cm = 100 x 10⁻⁶ = 10⁻⁴m³

Density of liquid = d= 1.8 x 10³ kg/m³

(i) The upthrust due to liquid

Upthrust= Buoyant Force B=Vdg

= 10⁻⁴ x 1.8×10³ x g

= 0.18g N

= 0.18 kgf

(ii) The weight of the body in liquid: So weight of Body in Liquid=W-B

= 5 kgf – 0.18 kgf

= 4.82 kgf

**Question 2. **A body weighs 450 gf in air and 310 gf when completely immersed in water. Find the following factors:

(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).

**Answer:**

Weight of the body in air, W = 450 gf = 450g dynes

Weight of the body in water, W/ = 310 gf = 310g dynes

Let, d be the density of the body, V be its volume. Let q be the density of water.

W = Vdg

450g = Vdg

Buoyant force, B = Vqg

B = Vg [q = 1 g/cm3]

Now, W/ = W – B

310g = 450g – Vg

V = 140 cm3

Loss in weight = Buoyant force = Vqg = 140 × 1 × g = 140g dynes = 140 gf**
**Again, upthrust = Buoyant force = 140 gf

**Exe-5A Upthrust and Archimedes Principle Numericals Answer Type**

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

**Page 123**

**Question 3. **You are provided with a hollow iron ball A of volume 15 cm^{3} 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.

(a) Find upthrust on each ball.

(b) Which ball will sink? Give a reason for your answer. (Density of iron = 8.0 g cm^{-3})

**Answer:**

**(Upthrust in Fluids Exe-5A Numericals ICSE)**

**Question 4. **A solid of density 5000 kg m^{-3} weighs 0.5 kgf in air. It is completely immersed in water of density 1000 kg m^{-3}. Calculate the apparent weight of the solid in water.

**Answer:**

mass of solid= 0.5 kgf

volume of solid = mass of solid / density of solid

= 0.5/5000

= 0.0001 m³

volume of water displaced = volume of solid = 0.0001 m³

mass of water displaced = density of water x volume of water displaced =

1000 x 0.0001 = 0.1 kgf

apparent weight = weight in air – weight of liquid displaced

= 0.5 kgf – 0.1 kgf

= 0.4 kgf

**Question 5. **Two spheres A and B, each of volume 100 cm^{3} are placed on water (density = 1.0 g cm^{-3}). The sphere A is made of wood of density 0.3 g cm^{-3} and the sphere B is made of iron of density 8.9 g cm^{-3}.

(a) Find:

(i) The weight of each sphere, and

(ii) The upthrust on each sphere.

(b) Which sphere will float? Give reason.

**Answer:**

Density of water = 1gcm-3

Density of sphere A = 0.3 gcm-3

Density of sphere B = 8.9 gcm-3

Volume of sphere A & B = 100 cm3

(a) (i)To find the weight of sphere A and B

Weight of sphere A = density of sphere A x volume of sphere x g

= 0.3 x 100 x g = 30gf

Weight of sphere B = density of sphere B x volume of sphere x g

= 8.9 x 100 x g = 890gf

(ii) To find upthrust on each sphere

Upthrust on sphere A = volume of sphere A x density of water x g

= 100 x 1 x g = 100gf

Upthrust on sphere B = volume of sphere B x density of water x g

= 100 x 1 x g = 100 gf

Upthrust acting on both the spheres is the same as the volume of spheres A and B inside water is the same

(b) Sphere A will float as the density of wood is lesser than that of water.

**Question 6. **The mass of a block made of certain material is 13.5 kg and its volume is 15 × 10^{-3} m^{3}.

(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}.

**Answer:**

**Question 7. **A piece of brass weighs 175 gf in air and 150 gf when fully submerged in water. The density of water is 1.0 g cm^{3}.

(i) What is the volume of the brass piece? (ii) Why does the brass piece weigh less in water?

**Answer:**

Weight of piece of brass in air = 175 gf

Weight pf piece of brass when fully immersed in water = 150 gf

Density of water = 1g cm-3

(i) Volume of brass price = Loss in weight = 175 – 150 = 25 cm3

(ii) The brass of price weighs less in water due to upthrust

**(Upthrust in Fluids Exe-5A Numericals ICSE)**

**Question 8. **A metal cube of edge 5 cm and density 9 g cm^{-3} is suspended by a thread so as to be completely immersed in a liquid of density 1.2 g cm^{-3}. Find the tension in thread. (Take g = 10 m s^{-2})

**Answer:**

Given , side of the cube = 5 cm

∴ volume of the cube = 5 × 5 × 5 = 125 cm^{3}

Mass of the cube = volume × density

= 125 × 9 = 1125 g

∴ weight of the cube = 1125 gf (downwards)

Upthrust on cube = weight of the liquid displaced

= volume of the cube × density of liquid × g

= 125 × 1.2 × g

= 150 gf (upwards)

Tension in thread = Net downward force

= Weight of cube – Upthrust on cube

= 1125 – 150 = 975 gf = 9.75 N

**Question 9. **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}.

**Answer:**

Volume of block of wood = 50 cm × 50 cm × 50 cm = 125000 cm^{3} = 0.125 m^{3}

Given , g = 9.8 m/s^{2}

Buoyant force = Vρg

= 0.125 × 1000 × 9.8 N

= 1225 N

**Question 10. **A body of mass 3.5 kg displaces 1000 cm^{3} of water when fully immersed inside it. Calculate: (i) the volume of body, (ii) the upthrust on body and (iii) the apparent weight of body in water.

**Answer:**

Mass of body = 3.5 kg

Weight of the body = 3.5 kgf

Volume of water displaced when body is fully immersed = 1000 cm^{3}

(i) Volume of body when fully immersed in liquid = Volume of water displaced

∴ Volume of body = 1000 cm^{3} or 0.001 m^{3}

(ii) Upthrust on body = Volume of body × Density of water × g

= 0.001 × 1000 × g

= 1 kgf

(iii) Apparent weight = True weight – Upthrust

= (3.5 – 1)

= 2.5 kgf

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

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