Tag: pressure in fluids

Questions Related to pressure in fluids

A body floats in a liquid if the buoyant force is

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

  1. zero

  2. less than its weight

  3. equal to its weight

  4. none of these

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Correct Option: B

A block of wood floats in water with (2/3)rd its volume submerged. The density of wood is 

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

  1. ${ 67gm/cm^{ 3 } }$

  2. ${ 6.7gm/cm^{ 3 } }$

  3. ${0. 67gm/cm^{ 3 } }$

  4. $7\times { 10 }^{ 3 }kg/{ m }^{ 3 }$

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Correct Option: C

Initially A cubical block of density  $\rho$  is floating in water. in a vessel Out of its height  $L ,$  length  $x$  is submerged in water. Suddenly vessel is kept in an elevator accelerating upwards with acceleration  $a.$   What is the length immersed in water?

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

  1. $L - X$

  2. $2 x$

  3. $x$

  4. $L$

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Correct Option: C

A ball falls through a liquid at a constant speed. It is acted upon by three forces: an upthrust, a drag-force and its weight.
Which statement is correct?

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

  1. The drag-force increases with increasing depth

  2. The drag-force is equal to the sum of the upthrust and weight

  3. The upthrust is constant with increasing depth

  4. The weight is greater than the sum of the drag-force and the upthrust

Show answer
Correct Option: C
Explanation:

A ball falls through a liquid at a constant speed .

It acted upon by the three force ,
1. up thrust : it is constant
2. drag force
3, weight ; it is downward
Hence, C is correct option.

A cube of wood supporting $200g$ mass just floats in water. When the mass is removed, the cube rises by $1cm$, the linear dimension of cube is:

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

  1. $10cm$

  2. $20cm$

  3. $10\sqrt{2}cm$

  4. $5\sqrt{2}cm$

Show answer
Correct Option: C
Explanation:

cube of wood supports$=200gm$
As, the mass is removed it rises by $1cm$
So, this implies that the weight of the $200g$ mass is equal to the weight of the water displaced by immersing $1cm$ of the cube,

Mathematically,
$a _{2}\times 1\times 1gm/cm^{3}\times g=g\times 200$
$a^{2}=10\sqrt{2}200cm^{2}$
$a=10\sqrt{2}cm$

A boat having a length of 3 metre and breadth 2 metre is floating on a lake. The boat sinks by one cm when a man gets on it. The mass of the man is:

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

  1. 60 kg

  2. 62 kg

  3. 72 kg

  4. 128 kg

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Correct Option: A
Explanation:

Amount of water displaced is $V=3\times 2\times 0.01=0.06m^3$
$\therefore F=1000\times 0.06 \times g=60g$
hence the man weighs 60kgs

A piece of iron of density $7800kg/m^3$ and volume $100cm^3$ is completely immersed in water. Calculate the upthrust on the iron piece.

[Take, $g=10m/s^2$.]

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

  1. $1N$

  2. $2.8N$

  3. $7.8N$

  4. $6.8N$

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Correct Option: A

if a block of wood is floating in a river water, then the apparent weight of the floating block is

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

  1. equal to the weight of the displaced water

  2. zero.

  3. greater than the weight of the displaced water

  4. equal to the actual weight of the block

Show answer
Correct Option: B
Explanation:
Apparent weight in calculated as
Apparent weight$=$(weight of body)$-$(Buoyancy force)
Where
weight of body$=$(mass of body)$\times$(Gravitational force)
Buoyancy force$=$weight of fluid displaced
for the floating body:-
weight of body$=$Buoyancy force
$\therefore$ The body floating and
apparent weight equals to zero.
$\therefore$ Answer is B.

A body of mass 50 kg has a volume 0.049 $m^3$ and is kept on a table. The buoyant force on it due to air is.

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

  1. 0.588 N

  2. 0.49 N

  3. 58.8 N

  4. 49 kgf

Show answer
Correct Option: D
Explanation:

since the mass is in equilibrium. So, the net downward force =buoyant force

buoyant force=50x9.8=49kgf

Calculate the upthrust acting on a ball of volume $\displaystyle 0.2{ m }^{ 3 }$ immersed in a liquid having density $\displaystyle { 1kg }/{ { m }^{ 3 } }$.

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

  1. 0.2f

  2. 2f

  3. 0.2g f

  4. 2g f

Show answer
Correct Option: C
Explanation:

Upthrust = weight of the liquid displaced by the submerged part of the body Upthrust = mass of liquid displaced x Acceleration due to gravity Upthrust = volume of liquid displaced x density of liquid displaced x Acceleration due to gravity,Since volume of solid immersed is equal to the volume of the liquid displaced, Upthrust = volume of solid immersed x density of liquid displaced x Acceleration due to gravity Upthrust = 0.2 x 1 x g = 0.2g f.