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

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

  1. Increases

  2. Decreases

  3. Remains same

  4. Depends on weather
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

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

  1. 100

  2. 1

  3. 20

  4. 105
Reveal answer Fill a bubble to check yourself
D Correct answer
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)

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

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

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

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

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

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

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

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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

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

 If the the height $(h)$ at which the atmospheric pressure is reduced to half. Find the value $\displaystyle h$.

  1. $\displaystyle h=\dfrac{0.693RT}{Mg}$.
  2. $\displaystyle h=\dfrac{6.93RT}{Mg}$.
  3. $\displaystyle h=\dfrac{693RT}{Mg}$.

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\displaystyle P=P _{0}e^{-Mgh/RT} $
But $\displaystyle P=0.5P _{0}$
Hence, $\displaystyle 0.5P _{0}=P _{0}e^{-Mgh/RT} $
$\displaystyle 0.5=e^{-Mgh/RT} $


Take natural logarithm on both sides.
$\displaystyle \ln0.5=e^{-Mgh/RT} $
$\displaystyle -0.693 =  {-Mgh/RT}$
Hence, $\displaystyle \displaystyle h=\dfrac{0.693RT}{Mg} $

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

A fully loaded Boeing aircraft has a mass of $33\times 10^{5}$ kg. Its total wing area is $500 m^2$. It is in level flight with a speed of $960 km/h$. (a) Estimate the pressure difference between the lower and upper surfaces of the wings. (b) Estimate the fractional increase in the speed of the air on the upper surface of the wing relative to the lower surface. The density of air is $\rho = 1.2 kg m^{-3}$ and $g = 9.81 m^{-2}$.

  1. $0.067$
  2. $0.075$
  3. $0.98$
  4. $0.88$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using Bernoulli's principle and the lift force equation (F = delta(P) * A), the pressure difference is calculated. Then, using the lift equation, the fractional speed increase is derived.

Multiple choice physics pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

Average density of air is:

  1. $\displaystyle 13600{ kg }/{ { m }^{ 3 } }$
  2. $\displaystyle 1.29{ kg }/{ { m }^{ 3 } }$

  3. Both

  4. All
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Average density of air is $\displaystyle 1.29{ kg }/{ { m }^{ 3 } }$ and the density of mercury as $\displaystyle 13600{ kg }/{ { m }^{ 3 } }$.