Tag: pressure in fluids

Questions Related to pressure in fluids

A bob's weight is measured by a spring balance. Its volume is $10 cm^3$. In vacuum it measures $80 g$. What does it weigh in water?

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. $70 g$

  2. $80 g$

  3. $90 g$

  4. $76 g$

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Correct Option: A
Explanation:

Weight of bob $= 80g/1000 N$ where $g$ is acceleration due to gravity

Weight of water displaced $= 10\times1\times g/1000 = 10g/1000 N$
Apparent weight$ = 80g/1000 - 10g/1000 = 70g/1000 N$
Weight measured $= 70/1000kg = 70 g$

Upthrust due to fluid equals

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. Volume of liquid displaced

  2. Mass of liquid displaced

  3. Weight of liquid displaced

  4. None of the above

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Correct Option: C
Explanation:

Upthrust equals weight of fluid displaced by the object.

A ship has volume of $1,50,000 m^3$. It submerges $10\%$ in water. Upthrust felt by it equals

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. $15 \times 10^6 N$

  2. $15 \times 10^7 N$

  3. $15 \times 10^8 N$

  4. $15 \times 10^5 N$

Show answer
Correct Option: B
Explanation:

Volume submerged$ = 15,000 m^3 $

Upthrust $= 15000m^3 \times 1000 kg/m^3 \times 10 m/s^2$
$=15 \times 10^7 N$

Consider a cylinder of height $h$ and Cross sectional area $A$ completely submerged in a fluid of density $\rho$. What is upthrust?

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. $Ah\rho g$

  2. $Ah\rho /g$

  3. $A\rho g$

  4. $Ah^2 \rho g$

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Correct Option: A
Explanation:

Upthrust = weight of fluid displaced

= Vol of fluid displaced x density of fluid x acc. due to gravity
$=Ah\rho g$

An object having relative density 0.56 is dropped in water. Will it float or sink in water?

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. Sink

  2. Float

  3. Depends on the density of water

  4. Unsure

Show answer
Correct Option: B
Explanation:

Explanation: the relative density of water is 1 and that of the object is less than 1. Thus the upthrust experienced by the object will be more than the weight of the object making it float on the surface of water.

A body of density equal to density of fluid is sinking at speed of $1 m/s$ at $t=0$. What is distance covered by object in $1s$? 

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. $0.5m$

  2. $1m$

  3. $0.75m$

  4. $0.875m$

Show answer
Correct Option: B
Explanation:

Upthrust = weight of the body since density of body equals density of fluid

Hence, Net force $= 0$ and acceleration$ = 0$
Distance = speed x time$ = 1m$

Analyse the given statements and choose the correct option.
Statement I: The buoyant force of water on a submerged wooden cube is greater than the buoyant force of water on a steel cube of equal volume.
Statement II: The buoyant force on a body is equal to the weight of the liquid displaced by the body.

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. Both statement I and statement II are correct and statement II is the correct explanation of statement I

  2. Both statement I and statement II are correct, but statement II is not the correct explanation of statement I

  3. Statement I is correct, but statement II is incorrect

  4. Statement I is incorrect, but statement II is correct

Show answer
Correct Option: D
Explanation:

Since buoyant force experienced by a body is equal to weight of liquid displaced by the body. Hence it remains same for all the bodies of equal volume.

The reading of a spring balance when a block is suspended from it in air is 60 newton. This reading is changed to 40 newton when the block is fully submerged in water. The specific gravity of the block must be therefore " 

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. 3

  2. 2

  3. 6

  4. 3/2

Show answer
Correct Option: A
Explanation:

Specific gravity or relative density of block is given as

$R.D.=\dfrac { mass\quad of\quad block }{ loss\quad in\quad mass\quad in\quad liquid } =\dfrac { 60 }{ 60-40 } $
$\boxed { R.D.=3 } $

The body when immersed fully or partially in a fluid, experiences an upward force, equal to ............. of displaced fluid.

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. Mass

  2. Weight

  3. Volume

  4. Area

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Correct Option: C

A solid sphere weighs $40\ N$ in water and $45\ N$ in water and $45N$ in a liquid of density $0.75$. The weigh of sphere in air will be

physics upthrust in fluids, archimedes' principle and floatation upthrust is equal to the weight of displaced liquid pressure in fluids buoyancy

  1. $60\ N$

  2. $53\ N$

  3. $50\ N$

  4. $80\ N$

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Correct Option: C