Atmospheric Pressure - Class VIII

A siphon works based on the pressure difference created by the difference in liquid levels between two vessels. If the levels are at the same height, there is no pressure difference to drive the flow.

Atmospheric pressure at sea level is $ 1.013 105 \times 10^5 $ Pa.

1 bar $ = 10^5$ Pa

Pressure of gas is same everywhere in the vessel.

• The atmospheric pressure is 1.013x${10}^5$ N/${m}^-2$

Otto von Guericke was a scientist of 17th century.  He invented a pump to extract air out of the vessel.

When pressure inside a sealed can becomes less than the atmospheric pressure, the atmospheric pressure pushes the surface of the can inside and the can is crushed.

When the pressure inside a sealed bottle exceeds the atmospheric pressure, it bursts out.

Crushing can experiment , Take an empty and absolutely clean Mobil oil can and put in it about 0.25 liter of water. Great the can in fire till all the air is expelled out and the steam comes out freely from its mouth.screw the mouth of the can with a lid and immediately remove it away from the fire .pour cold water on the can. It is found that the can gets crushed.the reason is that on pouring cold water, the steam changes into water ,thereby,causing a vacuum inside the can. Thus the tremendous atmospheric pressure,exerts pressure from outside and crushed the can.

$1 atm = 76 cm$ of Hg, $1 torr  1 mm$ of Hg, $1 bar = 10^5 Pa$.

Barometer is a scientific instrument which is used to caliberate pressure at different surroundings & pressure.

Fountain bottle, ping pong funnel as well as million doller bet are examples of atmospheric pressure.

760 mm Hg  $  =1$ atm

Pressure      $P = \dfrac{F}{A}$                $\implies P \propto F$

$Answer:-$ D

3) This is at a standard pressure of 1 atm. So, 22.4 atm pressure corresponds to 22.4 × 1.25 = 28 g  

For a sphere just submerged, the pressure varies with depth. The force on the lower half is greater than the force on the upper half due to the hydrostatic pressure gradient, resulting in a ratio of 5:1.

Since the mercury rises only $50cm$ it implies the rest of the excess atmospheric pressure is being countered by the pressure at the top of the tube.
So pressure at top=atmospheric pressure - $50cm$ of Hg=$(75-50)cm=25cm$ of Hg=$1/3\times 100kPa= 33.33kPa$

The work done by the system during a isobaric process is calculated as W = P * delta V. Given atmospheric pressure P = 1.013 * 10^5 Pa and volume change delta V = 3.34 - 2 * 10^-3 = 3.338 m^3. Multiplying these gives W = (1.013 * 10^5) * 3.338 approx 3.38 * 10^5 J, which is approximately 340 kJ.

Atmospheric pressure is highest at sea level because the entire column of air above exerts weight. It decreases as altitude increases.

Barometer measures atmospheric pressure (A-4). Chronometer measures time (B-3). Sextant measures angular distances (C-2). Quadrant measures altitudes/angles (D-1).

With increase in vertical height, the atmospheric pressure falls. Fall in pressure means that the temperature also falls. This is because pressure is directly proportional to Temperature and vice versa.

Pressure decreases with the increase in altitude.

atospheric pressure=760 mm of hg=76 cm of hg

The atmospheric pressure exists due to weight of atmospheric gases above a certain given height. As one goes high, the weight of atmosphere above decreases and so does the pressure. Thus for a balloon filled on ground, the pressure inside the balloon exceeds that outside and thus it bursts.

Air pressure decreases at high altitudes because the density of air decreases. It may cause the nose to bleed, especially if the individual has high blood pressure

Atmospheric pressure decreases with altitude due to decrease in height of the air column, which causes a linear decrease in atmospheric pressure

Air pressure increases when air descends and air pressure at sea level is more than at the mountain top, thus option D is correct.

Since at high altitude oxygen concentration is less in compare to that at sea level hence rate of ${ O } _{ 2 }$ consumption increases leading to increase in heart rate.

Those who successfully deal with altitude have strong hypoxic ventilatory drives.

The best conditions for an athlete to get adapted to is to live in less ${ O } _{ 2 }$ concentration region & train at high ${ O } _{ 2 }$ concentration region, i.e. live at high altitude & train at low altitude.

When a person reside at high altitude where oxygen concentration is very less, then their muscle fibre area decreases for maximization of oxygen carrying capacity.

$Answer:-$ A

The percentage of oxygen in the air decreases with increasing altitude.

Sulfur dioxide does not affect lung function in normal adults but causes bronchoconstriction in asthmatics.

Using Boyle's Law (P1V1 = P2V2) for the trapped air, the atmospheric pressure can be calculated based on the mercury column height and the tube dimensions.

When the tube is vertical, the pressure difference between the two air columns balances the weight of the mercury column. Using the ideal gas law and the change in volume, the displacement can be calculated.

Given T = T0 - ay, the dimension of 'a' must be temperature divided by length (K/L) to make the equation dimensionally consistent.

Using the ideal gas law in combined form, (P_1 * V_1) / T_1 = (P_2 * V_2) / T_2. Given P_1 = 76 cm Hg, V_1 = 2 m^3, T_1 = 27 + 273 = 300 K, P_2 = 38 cm Hg, and T_2 = -48 + 273 = 225 K. Solving for V_2 gives V_2 = (P_1 / P_2) * (T_2 / T_1) * V_1 = (76 / 38) * (225 / 300) * 2 = 2 * 0.75 * 2 = 3 m^3.

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.

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.

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

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.

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.

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

$\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} $

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.

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

If the barometric height is less than 76 cm,we can say that the air pressure has fallen,and if more than 76 cm ,we can say that air pressure has increased.

it is found that with the change in height, season, temperature etc the barometric height changes, This indicates change in air pressure.