Tag: common consequences of the atmospheric pressure

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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

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