Tag: fluid pressure

Questions Related to fluid pressure

A piece of iron [density 7.6$ \displaystyle gcm^{-3} $] sinks in mercury [density 13.6 $ \displaystyle gcm^{-3} $]. State whether true or false.

archimedes' principle fluid pressure properties of matter physics

  1. True

  2. False

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Correct Option: B
Explanation:

Since condition for sinking of a body of density $\sigma $ in a liquid of density S is 

                  $\sigma >S.$
& Since iron of density 7.69/cc is less lighter than density of mercury (density 13.6g/cc). Hence iron will float on mercury.

A piece of iron sinks in water but can float in mercury. True or false.

archimedes' principle fluid pressure properties of matter physics

  1. True

  2. False

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Correct Option: A
Explanation:

Conditions for sinking of a body of density $\sigma $ in a liquid of density S is 

           $\sigma \quad >\quad S$
hence iron sink in water & float in mercury as iron is lighter than mercury.

When an object is placed in a liquid whose density is lower than the object, the object will float. True or false.

archimedes' principle fluid pressure properties of matter physics

  1. True

  2. False

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Correct Option: B
Explanation:

a body of higher density would sink in a liquid of lower density 

so the given object would sink in this case
hence option (B) would be correct.

A body having density less than 1 $ \displaystyle gcm^{-3} $ floats in water. True or false

archimedes' principle fluid pressure properties of matter physics

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Conditions of a body of density $\sigma $ to float in liquid of density S is 

         $\sigma \quad \le \quad S$
hence a body of density 1gm/cc will float in water.

why does an iron rod sink in water?

archimedes' principle fluid pressure properties of matter physics

  1. The density of rod is more than that of water

  2. The volume of water is more than the weight of the object

  3. Both A and B

  4. None of the above

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Correct Option: A
Explanation:

The buoyant force depends on the density of liquid. When the density of the object is more than the density of the liquid, it sinks because the gravitational force acting on the object is more than the buoyant force of water.

State whether True or False.

Objects that sink will always displace their volume. 

archimedes' principle fluid pressure properties of matter physics

  1. True

  2. False

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Correct Option: A
Explanation:

Objects that sink will always displace the same volume of water as that of body which gives the net buoyant force applied on the body.

A body of mass 400 g has a volume of 300 cm$^3$. Will body sink in water or not? [Density of water = 1000 kg/m$^3$]

archimedes' principle fluid pressure properties of matter physics

  1. Sink

  2. Float

  3. Sink partly

  4. Float partly

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Correct Option: A
Explanation:
Given :     Density of water     $\rho _w = 1000$ $kg/m^3  = 1$ $g/(cm)^3$
Density of body        $\rho _s = \dfrac{M}{V} = \dfrac{400}{300} = 1.33$  $g/(cm)^2$
$\implies$     $\rho _s >\rho _w$
Thus the body will sink in water.

A slid floats in a liquid in a partially dipped position.

archimedes' principle fluid pressure properties of matter physics

  1. The solid exerts a force equal to its weight on the liquid

  2. The weight of the displaced liquid equals the weight of the solid

  3. The liquid exerts a force of buoyancy on the solid which is equal to the weight of the solid

  4. The weight of the dipped part of the solid is equal to the weight of the displaced liquid

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Correct Option: A,B,C
Explanation:

The force that solid exerts on liquid is its weight. Hence option A is correct.
Since the solid is stationary, the weight of solid is equal to the force exerted on it by liquid.
According to Archimedes' Principle, the buoyant force acting upwards on the solid is equal to the weight of the liquid displaced. Hence option B and C are correct.

A balloon lifting in air follows:

archimedes' principle fluid pressure properties of matter physics

  1. Law of gravitation

  2. Archimedes principle

  3. Laws of motion

  4. all of the above

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Correct Option: D
Explanation:

In a lifting balloon, force of gravitation acts downwards as on all other materials present on the earth, given by $mg$.

Also Archimedes' principle acts on the balloon to provide a buoyant force $V\rho g$ upwards, and greater in magnitude than the gravitational force downwards. (Where $\rho$ is the density of air)
Hence Newton's law of motion provides the acceleration of the balloon upwards, given by: $ma=V\rho g-mg$

When a body is wholly or partly immersed in a liquid it experiences. 

archimedes' principle fluid pressure properties of matter physics

  1. An up-thrust or down-thrust depending on the density of the liquid

  2. An up-thrust

  3. A down-thrust

  4. None of the above

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Correct Option: B
Explanation:

Whenever a body is wholly or partially immersed in a liquid it experience an upthrust or buoyant force.