Tag: pressure in fluids and atmospheric pressure

Questions Related to pressure in fluids and atmospheric pressure

Water rises up to a height $h _1$ in a capillary tube of radius $r$. The mass of the water lifted in the capillary tube is $M$. If the radius of the capillary tube is doubled, the mass of water that will rise in the capillary tube will be 

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $M$

  2. $2M$

  3. $\cfrac{M}{2}$

  4. $4M$

Show answer
Correct Option: B
Explanation:

Since we know that mass of water rise is proportional to volume of water.

Mass $\infty $ volume
$\dfrac { { M } _{ 1 } }{ { M } _{ 2 } } =\dfrac { { V } _{ 1 } }{ { V } _{ 2 } } =\dfrac { \pi { r } _{ 1 }^{ 2 }{ h } _{ 1 } }{ \pi { r } _{ 2 }^{ 2 }{ h } _{ 2 } } =\dfrac { { r } _{ 1 }^{ 2 }{ h } _{ 1 } }{ { r } _{ 2 }^{ 2 }{ h } _{ 2 } } \quad \rightarrow (1)$
and for capillary tube, we know that height $\alpha $ $\dfrac { 1 }{ radius } $
      So, $\dfrac { { h } _{ 1 } }{ { h } _{ 2 } } =\dfrac { { r } _{ 2 } }{ { r } _{ 1 } } \quad \rightarrow (II)$
     hence from (1) & (II)
     $\dfrac { { M } _{ 1 } }{ { M } _{ 2 } } =\dfrac { { r } _{ 1 }^{ 2 } }{ { r } _{ 2 }^{ 2 } } \times \dfrac { { r } _{ 2 } }{ { r } _{ 1 } } =\dfrac { { r } _{ 1 } }{ { r } _{ 2 } } $
     So ${ M } _{ 2 }=\dfrac { { r } _{ 2 } }{ { r } _{ 1 } } \times { M } _{ 1 }=\dfrac { 2r }{ r } \times M=2M$
              $\boxed { { M } _{ 2 }=2M } $

In a surface tension experiment with a capillary tube water rises up to $0.1 m$. If the same experiment is repeated on an artificial satellite which is revolving around the earth. The rise of water in a capillary tube will be

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $0.1 m$

  2. $9.8 m$

  3. $0.98 m$

  4. Full length of capillary tube

Show answer
Correct Option: D
Explanation:

If the experiment of capillary tube is performed in space then, it will rise to fall length of tube due to vaccum around it, i.e. no external pressure.

$5 g$ of water rises in the bore of capillary tube when it is dipped in water. If the radius of bore capillary tube is doubled, the mass of water that rises in the capillary tube above the outside water level is

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $1.5 g$

  2. $10 g$

  3. $5 g$

  4. $15 g$

Show answer
Correct Option: B

The height of water in a capillary tube of radius $2 cm$ is $4 cm$. What should be the radius of capillary, if the water rises to $8 cm$ in tube? 

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $1cm$

  2. $2 cm$

  3. $3 cm$

  4. $4 cm$

Show answer
Correct Option: A
Explanation:

Since we know that height of capillary rise in inversely proportional to radius of capillary.

i.e.    height $\alpha $ $\dfrac { 1 }{ radius } $
         $\dfrac { { h } _{ 1 } }{ { h } _{ 2 } } =\dfrac { { r } _{ 2 } }{ { r } _{ 1 } } $
         $\dfrac { 4 }{ 8 } =\dfrac { { r } _{ 2 } }{ 2 } \Rightarrow \boxed { { r } _{ 2 }=1cm } $

Two capillary tubes of the same material but of different radii are dipped in a liquid. The heights to which the liquid rises in the two tubes are $2.2 cm$ and $6.6 cm$. The ratio of radii of the tubes will be

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $1:9$

  2. $1:3$

  3. $9:1$

  4. $3:1$

Show answer
Correct Option: D
Explanation:

Since we know that height of capillary rise is inversely proportional to radii of tube, i.e.,

height $\propto \dfrac { 1 }{ radius } $

$\dfrac { { h } _{ 1 } }{ { h } _{ 2 } } =\dfrac { { r } _{ 2 } }{ { r } _{ 1 } } \Rightarrow \dfrac { 2.2cm }{ 6.6cm } =\dfrac { { r } _{ 2 } }{ { r } _{ 1 } } $

So, $\boxed { \dfrac { { r } _{ 1 } }{ { r } _{ 2 } } =3 } $

The height of water in a capillary tube of radius $2 cm$ is $4 cm$. What should be the radius of capillary, if the water rises to $8 cm$ in tube?

physics pressure in fluids and atmospheric pressure pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

  1. $1 cm$

  2. $0.1 cm$

  3. $2 cm$

  4. $4 cm$

Show answer
Correct Option: A
Explanation:

It is to be remembered that

height of a capillary rise $\propto \dfrac { 1 }{ radius\quad of\quad capillary } $
hence,
          $\dfrac { { h } _{ 1 } }{ { h } _{ 2 } } =\dfrac { { r } _{  2} }{ { r } _{ 1 } } $
          $\dfrac { 4 }{ 8 } =\dfrac { { r } _{ 2 } }{ 2 } \Rightarrow \boxed { { r } _{ 2 }=1cm } $

The boiling point of a liquid can be raised by

physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. Increasing pressure

  2. Decreasing pressure

  3. Increasing the heat supply

  4. Increasing the quantity of the liquid

Show answer
Correct Option: A
Explanation:

When water heats up the molecules move faster and faster and move farther apart, eventually becoming steam. When the pressure on the water is increased,  the molecules are more tightly held. This helps keep them from moving apart so it requires more heat to get them to "break free" and move apart. So, the higher the water pressure the higher the boiling point. 

Cooking is done fast in pressure cooker because

physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. The boiling point of water is lowered

  2. The boiling point of water is increased

  3. More pressure is the cooker cooks the food at 100C

  4. The boiling point remains the same but more steam cooks the food

Show answer
Correct Option: B
Explanation:

In a pressure cooker, as the pressure inside increases with time, the boiling point of water increases and hence is able to cook fast.

When the piston of a pump is pulled up, the pressure inside_____

physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. decreases

  2. increases

  3. remains same

  4. none of the above

Show answer
Correct Option: A
Explanation:

As the piston of pump is pulled up, the pressure inside decrees which leads to unbalance of pressures.

The air pressure inside out body is equal to the ____?

physics pressure in fluids and atmospheric pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

  1. in internal pressure

  2. atmospheric pressure

  3. both a and b

  4. none of the above

Show answer
Correct Option: B
Explanation:

The pressure inside our bodies is equal to the atmospheric pressure and cancels the pressure from outside. we do not get crushed under the atmospheric pressure.