Class 9 Pressure in Fluids and Atmospheric Pressure Mock Test (ICSE)

Topics in Pressure in Fluids and Atmospheric Pressure

• Thrust and pressure
• Pressure in a liquid column (p = h rho g)
• Pascal's law and the hydraulic machine
• Atmospheric pressure and its measurement
• Variation of atmospheric pressure with altitude

Pressure in Fluids and Atmospheric Pressure practice questions with answers

1. Q1Multiple choice·1 mark
   As we ascend to a higher altitude, how does the atmospheric pressure change?

   1. (a)It first decreases and then increases due to temperature variation.
   2. (b)It remains constant because air pressure is independent of altitude.
   3. (c)It increases because air density increases.
   4. (d)It decreases because the height of the air column above decreases.
   Show answer and step marks

   1. Correct option: (d) It decreases because the height of the air column above decreases.+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   The pressure at a depth $h$ in a liquid of density $\rho$ is given by $p = h\rho g$. On what factor does the liquid pressure NOT depend?

   1. (a)Surface area of the liquid container
   2. (b)Depth of the point inside the liquid
   3. (c)Density of the liquid
   4. (d)Acceleration due to gravity
   Show answer and step marks

   1. Correct option: (a) Surface area of the liquid container+1

   Answer: (a)
3. Q3Multiple choice·1 mark
   A force of $100 \text{ N}$ is applied normally on a surface of area $2 \text{ m}^2$. The pressure exerted on the surface is:

   1. (a)$50 \text{ N/m}^2$
   2. (b)$100 \text{ N/m}^2$
   3. (c)$0.02 \text{ N/m}^2$
   4. (d)$200 \text{ N/m}^2$
   Show answer and step marks

   1. Correct option: (a) $50 \text{ N/m}^2$+1

   Answer: (a)
4. Q4Multiple choice·1 mark
   Which of the following instruments is commonly used for weather forecasting to measure atmospheric pressure without the use of any liquid?

   1. (a)Simple barometer
   2. (b)Aneroid barometer
   3. (c)Fortin's barometer
   4. (d)Manometer
   Show answer and step marks

   1. Correct option: (b) Aneroid barometer+1

   Answer: (b)
5. Q5Short answer·2 marks
   State Pascal's law of transmission of pressure in liquids. Mention one practical application based on it.
   Show answer and step marks

   1. Statement: Pressure exerted anywhere in a confined liquid is transmitted equally and undiminished in all directions throughout the liquid.+1
   2. Application, any one of: hydraulic press; hydraulic lift (jack); hydraulic brakes of vehicles; or any other valid hydraulic machine.+1

   Answer: Pressure applied at any point of a liquid enclosed in a vessel is transmitted equally and undiminished in all directions. Application, any one of: hydraulic press, hydraulic lift (jack), hydraulic brakes.
6. Q6Long answer·4 marks
   (a) Define standard atmospheric pressure and state its value in SI units. [2] (b) Calculate the pressure exerted by a vertical mercury column of height $76 \text{ cm}$. Take the density of mercury as $1.36 \times 10^4 \text{ kg/m}^3$ and acceleration due to gravity $g = 9.8 \text{ m/s}^2$. [2]
   Show answer and step marks

   1. Definition: Standard atmospheric pressure is the pressure exerted by a mercury column of height $76\text{ cm}$ at $0^{\circ}\text{C}$ at sea level.+1
   2. Value in SI units: $1.013 \times 10^5 \text{ Pa}$ (or $\text{N/m}^2$).+1
   3. Formula for pressure: $p = h\rho g$, where $h = 0.76\text{ m}$, $\rho = 1.36 \times 10^4\text{ kg/m}^3$, and $g = 9.8\text{ m/s}^2$.+1
   4. Substitution and calculation: $p = 0.76 \times 1.36 \times 10^4 \times 9.8 = 1.013 \times 10^5 \text{ Pa}$.+1

   Answer: (a) Standard atmospheric pressure is the pressure exerted by a $76\text{ cm}$ column of mercury at $0^{\circ}\text{C}$ at sea level; its value is $1.013 \times 10^5\text{ Pa}$. (b) $p = h\rho g = 0.76 \times 1.36 \times 10^4 \times 9.8 = 1.013 \times 10^5\text{ Pa}$.

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