Tag: pressure in liquids and gases

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Questions Related to pressure in liquids and gases

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

1000 small balls each weighing 1 g strike one sq. cm of a area per second with a velocity of 100 m/sec in a normal direction and rebound with the same velocity. The pressure on the surface (in N/m$^2$) is :

  1. $2 \times 10^3$

  2. $4 \times 10^6$

  3. $10^7$

  4. $2 \times 10^6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Force = change in momentum per second. For one ball, delta p = 2mv. For 1000 balls, F = 1000 * 2 * (0.001 kg) * (100 m/s) = 200 N. Area = 1 cm^2 = 10^-4 m^2. Pressure = 200 / 10^-4 = 2 * 10^6 N/m^2.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

Identify the following shows the application of pressure in our everyday life?

  1. The blade of Ice-skating shoe is very sharp.

  2. It is easier to drive a sharp tipped nail into wood.

  3. Sharp knife cuts better.

  4. Foundation of high-rise building are kept narrow.
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

(A) if we decrease the area of the ice skating blades, then we mean to say we are increasing the pressure. We actually do this to increase pressure which reduces the chances of getting slipped.

(B) same concept is applicable in this as it was in the option (a). sharp tipped nail is having less area  and therefore exerts more pressure when it is tipped. so it easily gets tipped into the wood or even into the walls.
(C) same concept is in this option as well.
(D) same concept as it was in the previous 3 options. 

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

Choose the correct statement from the following?

  1. Pressure is same at all points in the horizontal plane.

  2. A liquid seeks its own level.

  3. The lateral pressure exerted by a liquid decreases with the increase in depth of the liquid.

  4. The upper surface of a stationary liquid is always horizontal.
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

(a) Pressure is same at all points in the horizontal plane. (correct)
(b) A liquid seeks its own level. (correct)
(c) The lateral pressure exerted by a liquid decreases with the increase in depth of the liquid. (wrong)
(d) The upper surface of a stationary liquid is always horizontal. (correct)

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

For the equlibrium AB (g) $\rightleftharpoons A (g) + B(g). K _p$ is equal to four times the total pressure. Calculate the number moles of A formed if one mol of AB is taken initially 

  1. 0.45

  2. 0.30

  3. 0.60

  4. 0.90
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For AB <=> A + B, let initial moles be 1. At equilibrium: AB (1-x), A (x), B (x). Total moles = 1+x. Partial pressures: P_AB = (1-x)/(1+x) * P_total, P_A = x/(1+x) * P_total, P_B = x/(1+x) * P_total. Kp = x^2 / (1-x^2) * P_total. Given Kp = 4 * P_total, so x^2 / (1-x^2) = 4. x^2 = 4 - 4x^2 => 5x^2 = 4 => x^2 = 0.8 => x = 0.894, approx 0.9.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

A same amount of same gas of temperature T are enclosed in a three identical vessel A,B, & C. The temperature of wall of three container is $T _A , T _B$ & $T _C (T _A > T _B > T _C)$ respectively. The pressure on wall of vessel. 

  1. $P _A &gt; P _B &gt; P _C$

  2. $P _A &lt; P _B &lt; P _C$

  3. $P _A = P _B = P _C$

  4. Deta's are insufficient to decide.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} PV=nRT \ P\propto T \ \therefore \, { T _{ A } }>{ T _{ B } }>{ T _{ C } } \ So, \ { P _{ A } }>{ P _{ B } }>{ P _{ C } } \ Hence, \ option\, \, A\, \, iscorrect\, answer. \end{array}$

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

A hole is made at the bottom of a tank filled with water. If total pressure at the bottom of the tank is three atmosphere, then the velocity of efflux at the bottom is (1 atm = $10^5 N/m^2$)

  1. $\sqrt{400} m/s$

  2. $\sqrt{200} m/s$

  3. $\sqrt{600} m/s$

  4. $\sqrt{500} m/s$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given,

$\begin{array}{l} P=1000kg/{ m^{ 3 } } \ P=3atm=3\times { 10^{ 5 } }N/{ m^{ 2 } } \ { P _{ 0 } }=1atm={ 10^{ 5 } }N/{ m^{ 2 } } \end{array}$
Pressure due to liquid column is 
$P - {P _0} =\rho gh$
velocity of flux $V = \sqrt {2gh} $
$\begin{array}{l} V=\sqrt { 2\dfrac { { \left( { p-{ P _{ 0 } } } \right)  } }{ \rho  }  }  \ =\sqrt { \dfrac { { 2\left( { 3\times { { 10 }^{ 5 } }-{ { 10 }^{ 5 } } } \right)  } }{ { 1000 } }  }  \ =\sqrt { \dfrac { { 4\times { { 10 }^{ 5 } } } }{ { 1000 } }  }  \ =\sqrt { 400 } m/s \end{array}$
Hence,
option $A$ is correct answer.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

Air is pumped into an automobile tube upto a pressure of $200 \mathrm{kP}  $ in the morning when the air temperature is $  22^{\circ} \mathrm{C}  $ . During the day, temperature rises to $ 42^{\circ} \mathrm{C}  $ and the tube expands by $2 \%  $ . The pressure of the air in the tube at this temperature, will be approximately

  1. $212 \mathrm{kPa} $

  2. $209 k P a $

  3. $206 \mathrm{kPa} $

  4. $200 \mathrm{kPa} $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\begin{array}{l} Given\, \, { P _{ 1 } }=200\, \, k\, pa \ { T _{ 1 } }=22^{ \circ  }C=273+22-295K \ { T _{ 2 } }=42^{ \circ  }C=273+42=315K \ PV=nRT \ \left( { \dfrac { { PV } }{ T }  } \right) ={ { constant } }\left[ \begin{array}{l} { { Since } }\, \, number\, \, of\, \, moles \ and\, \, R\, \, are\, \, { { constant } } \end{array} \right]  \ \dfrac { { { P _{ 1 } }{ V _{ 1 } } } }{ { { T _{ 1 } } } } =\dfrac { { { P _{ 2 } }{ V _{ 2 } } } }{ { { T _{ 2 } } } }  \ \dfrac { { 200\times 1 } }{ { 295 } } =\dfrac { { { P _{ 2 } }\left( { 1.02 } \right)  } }{ { 315 } }  \ { P _{ 2 } }=\dfrac { { 200\times 315 } }{ { 295\times 1.02 } } \, \, kPa \ = 209\, \, kPa \end{array}$

Option B.

Multiple choice physics pressure in liquids and gases pressure dependence on force and area concept of pressure pressure on surface

A person blows into open-end of a long pipe. As a result, a high pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe,

  1. a high pressure pulse starts traveling up the pipe, it the other end of the pipe is open.

  2. a low pressure pulse starts traveling up the pipe, if the other end of the pipe is open.

  3. a low pressure pulse starts traveling up the pipe, if the other end ot the pipe is closed.

  4. a high pressure pulse starts traveling up the pipe, if the other end of the pipe is closed.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A pressure wave undergoes a phase change of $ \pi$ radians on 

reflection from open end of no phase change occurs on reflection from 
closed end.