#### Chapters

Chapter 2: Motion in One Dimension

Chapter 3: Laws of Motion

Chapter 4: Pressure in Fluids

Chapter 5: Upthrust and Archimedes’ Principle

Chapter 6: Heat and Energy

Chapter 7: Energy Flow and Practices for Conservation of Resources

Chapter 8: Light

Chapter 9: Sound

Chapter 10: Electricity and Magnetism – 1

Chapter 11: Electricity and Magnetism – 2

## Chapter 5: Upthrust and Archimedes’ Principle

#### Practice Problem 1

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problem 1

A solid of density 2700 kgm’ and of volume 0.0015 m3 ¡s completely immersed in alcohol of density 800 kgm’.Calculate:

- Weight of solid in SI system.
- Upthrust on solid in SI system.
- Apparent weight of solid in alcohol.
- Will the apparent weight of solid be less or more, if it is immersed completely in brine solution? Give a reason, [g = 10 ms
^{-2}]

A stone of density 3000 kgm^{3} is lying submerged in water of density 1000 kgm^{3}. If the mass of stone in air is 150 kg, calculate the force required to lift the stone. [g = 10 ms^{2}]

A solid of area of cross-section 0.004 m^{2} and length 0.60 m is completely immersed in water of density 1000 kgm^{3}. Calculate:

- Wt of solid in SI system
- Upthrust acting on the solid in SI system.
- Apparent weight of solid in water.
- Apparent weight of solid in brine solution of density 1050 kgm
^{3}.

[Take g = 10 N/kg; Density of solid = 7200 kgm^{3}]

#### Practice Problem 2

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problem 2

A solid of density 7600 kgm^{3} is found to weigh 0.950 kgf in air. If 4/5 volume of solid is completely immersed in a solution of density 900 kgm^{3}, find the apparent weight of solid in a liquid.

A glass cylinder of length 12 x 10^{-2} m and area of crosssection 5 x 10^{-4} m^{2} has a density of 2500 kgm^{-3}. It is immersed in a liquid of density 1500 kgm^{-3}, such that 3/8. of its length is above the liquid. Find the apparent weight of glass cylinder in newtons.

#### Practice Problems 3

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 3

**A solid weighs 0.08 kgf in air and 0.065 kgf in water. Find**

(1) R.D. of solid

(2) Density of solid in SI system. [Density of water = 1000 kgm^{3}]

A solid of R.D. = 2.5 is found to weigh 0.120 kgf in water. Find the wt. of solid in air.

A solid of R.D. 4.2 is found to weigh 0.200 kgf in air. Find its apparent weight in water.

#### Practice Problems 4

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 4

A sinker is found to weigh 56.7 gf in water. When the sinker is tied to a cork of weight 6 gf, the combination is found to weigh 40.5 gf in water. Calculate R.D. of cork.

A solid lighter than water is found to weigh 7.5 gf in air. When tied to a sinker the combination is found to weigh .If the sinker alone weighs 72.5 gf in water, find R.D. of solid.

#### Practice Problems 5

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 5

An aluminium cube of side 5 cm and RD. 2.7 is suspended by a thread in alcohol of relative density 0.80. Find the tension in thread.

A cube of the lead of side 8 cm and R.D. 10.6 is suspended from the hook of a spring balance. Find the reading of spring balance. The cube is now completely immersed in sugar solution of R.D. 1.4. Calculate the new reading of spring balance.

#### Practice Problems 1

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 1

**A hollow cylinder of copper of length 25 cm and area of cross-section 15 cm ^{2}, floats in water with 3/5 of its length inside water. Calculate:**

(1) apparent density of a hollow copper cylinder.

(2) wt. of cylinder.

(3) extra force required to completely submerge it in water.

**A cork cut in the form of a cylinder floats in alcohol of density 0.8 gcm ^{-3}, such that 3/4 of its length is outside alcohol. If the total length of the cylinder is 35 cm and area of cross-section 25 cm^{2}, calculate:**

(1) density of cork

(2) wt. of cork

(3) extra force required to submerge it in alcohol

#### Practice Problems 2

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 2

A cylinder made of copper and aluminium floats in mercury of density 13.6 gem^{-3}, such that 0.26th part of it is below mercury. Find the density of solid.

An iceberg floats in sea water of density 1.17 g cm ^{3}, such that 2/9 of its volume is above sea water. Find the density of iceberg.

#### Practice Problems 3

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 3

A wooden block floats in alcohol with 3/8 of its length above alcohol. If it is made to float in water, what fraction of its length is above water? Density of alcohol is 0.80 g cm^{-3}.

A hollow metal cylinder of length 10 cm floats in alcohol of density 0.80 g cm^{-3}, with 1 cm of its length above it. What length of cylinder will be above copper sulphate solution of density 1.25 g cm^{-3}?

#### Practice Problems 4

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 4

What fraction of an iceberg of density 910 kgm^{-3} will be above the surface of sea water of density 1170 kgm^{-3 }?

What fraction of metal of density 3400 kgm^{-3} will be above the surface of mercury of density 13600 kgm^{-3}, while floating in mercury?

#### Practice Problems 5

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 5

A balloon of volume 1000 m^{3} is filled with a mixture of hydrogen and helium of density 0.32 kgm^{-3}. If the fabric of balloon weighs 40 kgf and the density of cold air is 1.32 kgm^{-3}, find the tension in the tope, which is holding the balloon to ground.

A balloon of volume 800 cm^{3} is filled with hydrogen gas of density 9 x 10^{-5} gem^{-3}. If the empty balloon weighs 0.3 gf and density of air is 1.3 x 10^{-3} gem^{-3}, calculate the lifting power of balloon.

A balloon of volume 120 m^{3} is filled with hot air, of density 38 kg^{-3}. If the fabric of balloon weighs 12 kg, such that additional equipment of wt. x is attached to it, calculate the magnitude of Density of cold air is 1.30 kgm^{-3}.

#### Practice Problems 6

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Practice Problems 6

A test tube weighing 17 gf, floats in alcohol to the level P. When the test tube is made to float in water to the level P, 3 gf of the lead shots are added in it. find the R.D. of alcohol.

A test tube loaded with lead shots, weighs 150 gf and floats upto the mark X in water. The test tube is then made to float in alcohol. It is found that 27 gf of lead shots have to be removed, so as to float it to level X. Find R.D. of alcohol.

#### Objective Questions

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Objective Questions

**Select the correct option:**

The force experienced by a body when partially or fully immersed in water is called:

aparent weight

upthrust

down thrust

none of these

**Select the correct option:**

When a body is floating in a liquid:

The weight of the body is less than the upthrust due to immersed part of the body

The weight of body is more than the upthrust due to the immersed part of the body

The weight of body is equal to the upthrust due to the immersed part of the body

none of the above

**Select the correct option:**

With the increase in the density of the fluid, the upthrust experienced by a body immersed in it:

decreases

increases

remains same

none of these

**Select the correct option:**

The apparent weight of a body in a fluid is:

equal to weight of fluid displaced

volume of fluid displaced

difference between its weight in air and weight of fluid displaced

none of the above

**Select the correct option:**

The phenomenon due to which a solid experiences upward force when immersed in water is called:

floatation

buoyancy

density

none of these

**Select the correct option:**

When an object sinks in a liquid, its:

buoyant force is more than the weight of object

buoyant force is less than the weight of an object

buoyant force is equal to the weight of the object

none of the above

**Select the correct option:**

The SI unit of density is:

gem

^{-3}kgem

^{-3}kgm-

^{3}gm-

^{3}

**Select the correct option:**

When a body is wholly or partially immersed in a liquid, it experiences a buoyant force which is equal to:

volume of liquid displaced by it

weight of liquid displaced by it

both volume of liquid displaced by it and weight of liquid displaced by it

none of the above

**Select the correct option:**

The ratio between the mass of a substance and the mass of an equal volume of water at 4°C is called:

relative density

density

weight

pressure

**Select the correct option:**

A body has density 9.6 gcm ^{-3}. Its density in SI system is:

96 kgm

^{-3}960 kgm

^{-3}9600 kgm

^{-3}96,000 kgm

^{-3 }

#### Subjective Questions

### Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 Chapter 5 Upthrust and Archimedes’ Principle Subjective Questions

A wooden block floats in water with two-third of its volume submerged.

(a) Calculate the density of wood.

(b) When the same block is placed in oil, three-quarters of its volume is immersed in oil. Calculate the density of oil.

A metal cube of 5cm edge and relative density 9 is suspended by a thread so as to be completely immersed in a liquid of relative density 1.2. Find the tension in the thread.

A weather forecasting plastic balloon of volume 15 m^{3} contains hydrogen of density 0.09 kg m^{-3}. The volume of equipment carried by the balloon is negligible compared to its own volume. The mass of an empty balloon alone is 7.15 kg. The balloon is floating in air of density of 1.3 kg m^{-3}. Calculate:

(i) The mass of hydrogen in the balloon,

(ii) The mass of hydrogen and balloon,

(iii) The total mass of hydrogen, balloon and equipment if the mass of equipment is x kg,

(iv) The mass of air displaced by balloon and

(v) The mass of equipment using the law of floatation.

State the principle of floatation.

The mass of a block made of certain material is 1.35 kg and its volume is 1.5 x 10^{-3} m^{3}.

- Find the density of block.
- Will this block float or sink? Give reasons for your answer.

State the Archimedes' principle.

A block of mass 7 kg and volume 0.07 m^{3} floats in a liquid of density 140 kg/m^{3}. Calculate:

- Volume of block above the surface of liquid.
- Density of block.

A body whose volume is 100 cm^{3} weighs 1 kgf in air. Find its weight in water.

Why is it easier to swim in sea water than in river water?

Why does a ship make of iron not sink in water, while an iron nail sinks in it?

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.

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

A body floats in a liquid with a part of it submerged inside the liquid. Is the weight of floating body greater than, equal to or less than the upthrust?

A sinker is first weighed alone under water. It is then tied to a cork and again weighed under water. In which of the two cases weight under water is less and why?

A solid weighs 105 kgf in air. When completely immersed in water, it displaces 30,000 cm^{3} of water, calculate relative density of solid.

A test tube loaded with lead shots weighs 25 gf and floats upto the mark X in water. When the test tube is made to float in brine solution, it needs 5 gf more of lead shots to float upto level X. Find the relative density of brine solution.

**A wooden block is weighed with iron, such that combination just floats in the water at room temperature. State your observations when:**

(1) water is heated above room temperature

(2) water is cooled below 4°C. Give reasons to your answers in (1) and (2).

A rubber ball floats in water with 2/7 of its volume above the surface of the water. Calculate the average relative density of the rubber ball.

A cube of ice whose side is 4.0 cm is allowed to melt. The volume of water formed is found to be 58.24 cm^{3}. Find the density of ice.

A jeweller claims that he makes ornaments of pure gold that has a relative density of 19.3. He sells a bangle weighing 25.25 gf to a person. The clever customer weighs the bangle when immersed in water and finds that it weighs 23.075 gf in water. With the help of suitable calculations, find out whether the ornament is made of pure gold or not.

[Hint : calculate R.D. of material of bangle which comes out to be 11.6].

When a piece of ice floating in water melts, the level of water inside the glass remains same. Explain.

An inflated balloon is placed inside a big glass jar which is connected to an evacuating pump. What will you observe when the evacuating pump starts working? Give a reason for your answer.

A trawler is fully loaded in sea water to maximum capacity. What will happen to this trawler, if moved to river water? Explain your answer.

A body of mass 50 g is floting in water. What is the apparent weight of body in water? Explain your answer.

**A body of mass ‘m’ is floating in a liquid of density ‘p’**

what is the apparent weight of body?

**A body of mass ‘m’ is floating in a liquid of density ‘p’**

what is the loss of weight of body?

A block of wood of volume 25 cm^{3} floats in water with 20 cm^{3} of its volume immersed in water.

Calculate:

(1) density of wood

(2) the weight of block of wood.

A solid body weighs 2.10 N. in air. Its relative density is 8.4. How much will the body weigh if placed

(1) in water,

(2) in liquid of relative density 1.2?

## Chapter 5: Upthrust and Archimedes’ Principle

## Goyal Brothers Prakashan solutions for Class 9 A New Approach to ICSE Physics Part 1 chapter 5 - Upthrust and Archimedes’ Principle

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Concepts covered in Class 9 A New Approach to ICSE Physics Part 1 chapter 5 Upthrust and Archimedes’ Principle are Change of Pressure with Depth, Transmission of Pressure in Liquids, Pascal's Law, Atmospheric Pressure, Buoyancy, Archimedes' Principle, Floatation - Principle of Floatation, Relation Between the Density of a Floating Body, Determination of Relative Density of a Solid, Introduction of Fluid.

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