Atmospheric Pressure

Q. Toricelli’s barometer used mercury. Pascal duplicated it using French wine of density 984 kg m¯³. Determine the height of the wine column for normal atmospheric pressure.

Q.

During the melting of a slab of ice at 273 K at atmospheric pressure

1. Positive work is done by ice-water system on the atmosphere

2. Positive work is done on the ice-water system by the atmosphere

3. The internal energy of the ice-water system increases

4. The internal energy of the ice-water system decreases

Q. 32.A uniform rope of mass M and length L is placed on a smooth horizontal surface. a horizontal force f is acting at one end of rope calculate the tension in the Rope at a distance x as shown

Q. The atmospheric pressure at a place is 105 Pa. If tribromomethane (specific gravity = 2.9) be employed as the barometric liquid, the barometric height is

Q. A manometer reads the pressure of a gas in an enclosure as shown in Fig. 10.25 (a) When a pump removes some of the gas, the manometer reads as in Fig. 10.25 (b) The liquid used in the manometers is mercury and the atmospheric pressure is 76 cm of mercury. (a) Give the absolute and gauge pressure of the gas in the enclosure for cases (a) and (b), in units of cm of mercury. (b) How would the levels change in case (b) if 13.6 cm of water (immiscible with mercury) are poured into the right limb of the manometer ? (Ignore the small change in the volume of the gas).

Q.

Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid because

1. Force of surface tension predominates the force of gravity

2. Force of gravity and force of surface tension act in the same direction and are equal

3. Force of surface tension is equal and opposite to the force of gravity

4. Force of gravity predominates the force of surface tension

Q. In the manometer as shown, $2$ immiscible fluids - mercury $(\rho =13600{\text{kg/m}}^3)$ and water $(\rho =1000{\text{kg/m}}^3)$ are used as manometric fluids. The water end is exposed to the atmosphere $\left(100\text{kPa}\right)$ and the mercury end is exposed to a gas. At this position, the interface between the fluids is at the bottom most point of the manometer. The value of $h$ is found to be $9.45\text{m}$. The height of the mercury column is given to be $75\text{cm}$. Find the gauge pressure of the gas. $(g=9.8{\text{m/s}}^2)$

1. $100\text{kPa}$
2. $50\text{kPa}$
3. $200\text{kPa}$
4. $0\text{kPa}$

Q.

The value of g at a place decreases by 2%. The barometric height of mercury

1. Increases by 2%

2. Decreases by 2%

3. Remains unchanged

4. Sometimes increases and sometimes decreases

Q. A barometer kept in an elevator accelerating upward reads 76 cm. The air pressure in the elevator is
(a) 76 cm
(b) < 76 cm
(c) > 76 cm
(d) zero

Q. A thin rod of mass M and length L is hinged at its upper end, and released from rest from horizontal position. The tension at a point located at a distance L/3 from the hinge point, when the rod becomes vertical will be. (in terms of m and g).

Q. A barometer is constructed with its tube having radius 1.0 mm. Assume that the surface of mercury in the tube is spherical in shape. If the atmospheric pressure is equal to 76 cm of mercury, what will be the height raised in the barometer tube? The contact angle of mercury with glass = 135° and surface tension of mercury = 0.465 N m⁻¹. Density of mercury = 13600 kg m⁻³.

Q. Two separate air bubbles $\text{A}$ and $\text{B}$ of radii $0.004\text{m}$ and $0.002\text{m}$ formed of the same liquid surface tension $0.07\text{N/m}$ come together to form a double bubble. Find the radius and the sense of curvature of the internal film surface common to both the bubbles.

1. $0.004\text{m}$
2. $4\text{m}$
3. $0.4\text{m}$
4. $0.0004\text{m}$

Q. Two separate air bubbles $\text{A}$ and $\text{B}$ of radii $0.004\text{m}$ and $0.002\text{m}$ formed of the same liquid surface tension $0.07\text{N/m}$ come together to form a double bubble. Find the radius and the sense of curvature of the internal film surface common to both the bubbles.

1. $0.004\text{m}$
2. $4\text{m}$
3. $0.4\text{m}$
4. $0.0004\text{m}$

Q. Select the correct statement :-
(i) Barometer is used to measure atmospheric pressure
(ii) Manometer is used to measure gauge pressure of a fluid inside a container

1. (i) Only
2. (ii) Only
3. Both (i) & (ii)
4. None of these

Q. In the manometer as shown, $2$ immiscible fluids - mercury $(\rho =13600{\text{kg/m}}^3)$ and water $(\rho =1000{\text{kg/m}}^3)$ are used as manometric fluids. The water end is exposed to the atmosphere $\left(100\text{kPa}\right)$ and the mercury end is exposed to a gas. At this position, the interface between the fluids is at the bottom most point of the manometer. The value of $h$ is found to be $9.45\text{m}$. The height of the mercury column is given to be $75\text{cm}$. Find the gauge pressure of the gas. $(g=9.8{\text{m/s}}^2)$

1. $100\text{kPa}$
2. $50\text{kPa}$
3. $200\text{kPa}$
4. $0\text{kPa}$

Q. A barometer kept in an elevator reads 76cm when the elevator is accelerating upwards.The most likely pressure inside the elevator (in cm of Hg)

Q. Is the direction of absolute pressure upwards? Is it opposite of the pressure of the atmosphere and the fluid

Q. Consider the barometer shown in figure. If a small hole is made at a point P in the barometer tube, will the mercury come out from this hole?

Q. A student wants to find the absolute pressure of water at a point below the surface of water. He has a barometer and a manometer pressure gauge. The barometer reads $1.3152\text{bar}$ whereas the manometer pressure gauge reads $0.3152\text{bar}$. What is the absolute pressure? (Assume that pressure at one end of the manometer is atmospheric.)

1. $1\text{bar}$
2. $1.6304\text{bar}$
3. $0.3152\text{bar}$
4. $1.3152\text{bar}$

Q. Suppose the pressure at the surface of mercury in a barometer tube is P₁ and the pressure at the surface of mercury in the cup is P₂.
(a) P₁ = 0, P₂ = atmospheric pressure
(b) P₁ = atmospheric pressure P₂ = 0
(c) P₁ = P₂ = atmospheric pressure
(d) P₁ = P₂ = 0

Q.

An inverted tube barometer is kept in a lift moving vertical upward with an acceleration 'a'. The density of mercury is $\rho$ and acceleration due to gravity is g. If the atmospheric pressure be $P_o$ then

1. Height of the mercury column in the lift will be $\frac{P_o}{\rho (g+a)}$

2. Height of the mercury column in the lift will be $\frac{P_o}{\rho (g-a)}$

3. Height of the mercury column in the lift will be $\frac{P_o}{\rho g}$

4. Height of the mercury column in the lift will be $\frac{P_o}{\rho a}$

Q. Figure shows a capillary tube of radius r dipped into water. If the atmospheric pressure is P₀, the pressure at point A is
(a) P₀
(b) $P_0+\frac{2S}{r}$
(c) $P_0-\frac{2S}{r}$
(d) $P_0-\frac{4S}{r}$

Q.

Why do bubbles in a bear glass expand as they rise towards the surface?

Q.

If the air on Earth's surface is replaced with water, then to what extent the water level must rise so as to maintain the same pressure on Earth's surface? [Assume nothing above water surface. given g = 10 m/s², density of water = 1000 kg/m³.

1. 5 m

2. 10 m

3. 20 m

4. 15 m

Q. rain is falling at the speed of 25\sqrt3m/s vertically .the wind blows west to east at a speed of 25m/s.fiend the velocity of rain as experienced by a person s†an ding on the gr

Q. Solve this:
Q.4. Variation of atmospheric pressure with height from earth is
(1) Linear
(2) Parabolic
(3) Exponential
(4) Hyperbolic

Q.

Why we cant dig a well from one end of the earth to another?

Q. Solar radiation of intensity $1.5{\text{kW/m}}^2$ is incident on a perfectly black surface, making an angle of ${30}^{\circ }$ with the surface. What is the pressure experienced by the surface?

1. $0.25\times {10}^{-6}{\text{N/m}}^2$
2. $0.25\times {10}^{-8}{\text{N/m}}^2$
3. $1.25\times {10}^{-8}{\text{N/m}}^2$
4. $1.25\times {10}^{-6}{\text{N/m}}^2$

Q. Does it matter if one uses gauge instead of absolute pressures in applying Bernoulli's equation ? Explain.

Q.

When impurity is added to a liquid, its surface tension

1. decreases

2. first decreases and then increases

3. increases

4. remains same