Tag: pressure in fluids and atmospheric pressure

Questions Related to pressure in fluids and atmospheric pressure

one -meter long tube closed at both the ends is lying horizontally. A mercury column of length 0.1 m is filled in its middle and in rest in two parts air is filled at atmospheric pressure. when the tube is turned to verticle position then displacement of mercury column will be 

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. 29m

  2. 0.29m

  3. 0.029m

  4. 2.9m

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Correct Option: C

In troposphere, temperature varies linearly with elevation as $T=T _0-ay$, where $T _0$ is the temperature at the earth surface, then:

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. the pressure does not change with elevation in troposphere

  2. the variation of pressure with elevation is linear

  3. the dimension of $a$ is $[M^0L^{-1}0]$

  4. the pressure is independent of variation with temperature in the given situation

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Correct Option: C

A $2-m3$ weather balloon is loosely filled with helium at $1\ atm (76\ cm\ Hg)$ and at $27^{\circ}C$. At an elevation of $20,000\ ft$, the atmospheric pressure is down to $38\ cm\ Hg$ and the helium has expanded, being under no constraint from the confining bag. If the temperature at this elevation is $-48^{\circ}C$, the gas volume (in $m3)$ is

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. $3$

  2. $4.28$

  3. $2$

  4. $2.5$

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Correct Option: C

The atmospheric pressure on a hill can be ___ $cm$ of mercury.

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. $76$

  2. $70$

  3. $79$

  4. can't say

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Correct Option: B
Explanation:

Pressure at the surface is $76 cm$ of mercury , Also as we up on a hill pressure decrease ,hence pressure will be less than $76 cm$ of mercury.

So the possible answer is $70 cm$ of mercury.

How does pressure vary as we come from mountain top to sea level?

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Increases

  2. Decreases

  3. Remains same

  4. Depends on weather

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Correct Option: A
Explanation:

Answer is A.

For every meter we descend, the pressure per square meter increases by the weight of air per cubic meter at the height where we are.

76 cm of mercury column exerts a pressure equal to that exerted by:

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. 7920 m of air column

  2. 105 m of air column

  3. 1 cm of air column

  4. 1.29 m of air column

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Correct Option: A
Explanation:

1 cm of mercury column exerts pressure=105 m of air column
76cm of mercury column exerts pressure =105 x 76 cm = 7980 m of air column

______ m of air column ,on an average ,will exert as much pressure as 1 cm column of mercury.

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. 100

  2. 1

  3. 20

  4. 105

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Correct Option: D
Explanation:

We may write, 
Height of air column $\times$ Density of air $=$ Hight of mercury column $\times$ Density of mercury
Height of air column x $\displaystyle 1.29{ kg }/{ { m }^{ 3 } }=0.01m\times 13600{ kg }/{ { m }^{ 3 } }$
Height of air column =$\frac{136}{1.29}=105m$ (approx)

It takes much longer to cook food in the hills than in the plains, because

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. in the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than $100^oC$ causing an increase in cooking time

  2. due to low atmospheric pressure on the hills, the water boils at a temperature higher than $100^oC$ and therefore water takes longer to boil

  3. in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere

  4. in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking

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Correct Option: A
Explanation:

Since decrease in air pressure causes decrease in boiling temperature, because of which it takes more time to cook at hilly areas or high altitudes.

Water boils at a lower temperature than $100^o$C on a hill station, because.

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Pressure is lower at high altitudes

  2. Temperature is lower at high altitudes

  3. Water vapours are less at high altitudes

  4. There is cloud formation at high altitudes

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Correct Option: A
Explanation:

Pressure decreases as we go up due to which boiling point also decreases. So water boils at a lower temperature than $100^{\circ C}$ on hill station.

Why does water boil below $100^o$C at higher altitudes?

physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Pollution-free air at higher altitudes increases the calorific value of fuel used

  2. Water available at higher altitudes is purer than that in the plains

  3. There is lesser dissipation of heat at higher altitudes

  4. The atmospheric pressure at higher altitudes is low as compared to that at sea level

Show answer
Correct Option: D
Explanation:

As the atmospheric pressure is low at higher altitudes is compared to that sea level which causes decrease in boiling point as pressure is inversely proportional  the temperature. So, water does boil below $100^{\circ }C$ at higher altitude