Tag: pressure in fluids and atmospheric pressure

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Questions Related to pressure in fluids and atmospheric pressure

Multiple choice 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

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 

  1. $M$
  2. $2M$
  3. $\cfrac{M}{2}$
  4. $4M$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 } $

Multiple choice 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

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

  1. $0.1 m$
  2. $9.8 m$
  3. $0.98 m$

  4. Full length of capillary tube
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice 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

$5 g$ 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

  1. $1.5 g$
  2. $10 g$
  3. $5 g$
  4. $15 g$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The height of water in a capillary tube is inversely proportional to the radius (h = 2T / rρg). If the radius is doubled, the height is halved. Since mass m = πr^2 h ρ, and h is proportional to 1/r, then m is proportional to r^2 * (1/r) = r. Doubling the radius doubles the mass.

Multiple choice 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

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? 

  1. $1cm$
  2. $2 cm$
  3. $3 cm$
  4. $4 cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 } $

Multiple choice 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

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

  1. $1:9$
  2. $1:3$
  3. $9:1$
  4. $3:1$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 } $

Multiple choice 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

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?

  1. $1 cm$
  2. $0.1 cm$
  3. $2 cm$
  4. $4 cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
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 } $

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

The boiling point of a liquid can be raised by

  1. Increasing pressure

  2. Decreasing pressure

  3. Increasing the heat supply

  4. Increasing the quantity of the liquid
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

Cooking is done fast in pressure cooker because

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. in internal pressure

  2. atmospheric pressure

  3. both a and b

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
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.