Tag: fluid pressure

Questions Related to fluid pressure

Why an iron nail floats on mercury but it sinks in water?

archimedes' principle fluid pressure properties of matter physics

  1. Density of iron is more than that of mercury, but less than that of water.

  2. Density of iron is less than that of mercury, but more than that of water.

  3. Density of iron is less than that of mercury and water

  4. Density of iron is more than that of mercury, water.

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Correct Option: B
Explanation:

This is because density of mercury is more than that of water.
An object floats on a liquid, if its density is lower than that of the liquid. 
The density of iron nail is more than that of the water but less than that of mercury.

Buoyant force is directed

physics floatation buoyancy fluid pressure option b: engineering physics

  1. upwards

  2. downwards

  3. sideways

  4. at ll directions

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Correct Option: A
Explanation:

As evident from Archimedes' principle, buoyant force is the force applied upward on any object by a fluid.

When a solid is completely immersed in a fluid, the apparent loss of weight of solid is _______ volume of fluid displaced 

physics floatation buoyancy fluid pressure option b: engineering physics

  1. more than

  2. less than

  3. equal to

  4. cant say

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Correct Option: C
Explanation:

From the principle of Archimedes, loss of weight is equal to the weight of the liquid displaced.

When a body is fully immersed in a liquid the apparent loss in the weight of body is equal to :

physics floatation buoyancy fluid pressure option b: engineering physics

  1. volume of liquid displaced by the body

  2. density of the liquid

  3. weight of liquid displaced by the body

  4. none of these

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Correct Option: C
Explanation:

According to Archimedes principle, the weight of water displaced is equal to the weight of immersed part.For a solid floating in a liquid, its weight acting vertically down at its centre of gravity is equal to the weight of the liquid displaced by the immersed part of the solid acting vertically up at its centre of buoyancy. In the floating condition, the apparent weight and the apparent density of the solid are zero and the body is said to be weightless.

State whether the weight of an iron sinker with cork combined in water will be more or less than that of the iron sinker alone in water. 

physics floatation buoyancy fluid pressure option b: engineering physics

  1. Less

  2. More

  3. Same

  4. None of the above

Show answer
Correct Option: A
Explanation:

The weight of an iron sinker with cork combined in water will be less than that of the iron sinker alone in water.
This is because upthrust on cork due to water (when completely immersed) is greater than its weight.

An incompressible liquid of density $\rho$ is contained in a vessel of uniform cross-sectional area $A$. If then atmospheric pressure is $p$, then the force acting on a horizontal plane of area a situated at a depth $d$ in liquid is given by

physics option b: engineering physics buoyancy floatation fluid pressure

  1. $Ap+apgd$

  2. $\dfrac { p }{ A } +\dfrac { \rho gd }{ a }$

  3. $\dfrac { p+\rho gd }{ a }$

  4. $a\left( \rho\ gd+p \right)$

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Correct Option: D

A gas is enclosed in a rectangular vessel. $20 \times 10^23$ molecules of the gas strike a well of the vessel normally per second, with a velocity of 250m/s and rebound with the same speed in the opposite direction. What is the force exerted by the gas on the wall if the mass of each molecule is $5 \times 10^-23$ g ? 

physics option b: engineering physics buoyancy floatation fluid pressure

  1. 50 N

  2. 40 N

  3. 75 N

  4. 25 N

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Correct Option: A

A pump is required to lift 1000 kg of water per minute from a well 20 m deep and eject it at a rate of 20 $ms^-1$. What (horsepower engine is required for the purpose of lifting water)?

physics option b: engineering physics buoyancy floatation fluid pressure

  1. $4.46 HP$

  2. $4.36 HP$

  3. $3.96 HP$

  4. $8.85 HP$

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Correct Option: A

The branch of physics which deals with the study of fluids at rest is called :

physics option b: engineering physics buoyancy floatation fluid pressure

  1. statistics

  2. hydrostatics

  3. hydrodynamics

  4. thermometry

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Correct Option: B
Explanation:

The branch of physics which deals with the study of fluids at rest is called hydrostatics.

Hydro stands for liquids and statics is for the fluid at rest.

KE per unit volume is E. The pressure exerted by the gas is given by:

physics option b: engineering physics buoyancy floatation fluid pressure

  1. $\displaystyle \frac {E}{3}$

  2. $\displaystyle \frac {2E}{3}$

  3. $\displaystyle \frac {3E}{2}$

  4. $\displaystyle \frac {E}{2}$

Show answer
Correct Option: B
Explanation:

Pressure exerted by gas is given by $P=\dfrac{1}{3}\rho v^2$

where $v$ is the velocity of gas particles, $\rho $ is the density of gas.
Kinetic energy per unit volume$=E=\dfrac{\dfrac{1}{2}mv^2}{V}=\dfrac{1}{2}\rho v^2$
Thus $P=\dfrac{2}{3}(\dfrac{1}{2}\rho v^2)=\dfrac{2E}{3}$