Test: Pressure - UPSC MCQ

Pressure is defined as the force applied per unit area. It is the ratio of force to the area over which the force is distributed.

The SI unit of pressure is the Pascal (Pa). It is named after the French mathematician and physicist Blaise Pascal.

The pressure exerted by a fluid depends on several factors:

• Density of the fluid
• Depth of the fluid
• Acceleration due to gravity

P_A = ρgh_A
P_B = ρgh_B

However, the area of the surface on which the fluid acts does not affect the pressure. Pressure is defined as force per unit area, and in a fluid, it is determined by the factors listed above, not the surface area itself.

Atmospheric pressure decreases with increasing altitude. This is because the weight of the air above decreases as altitude increases.

A hydraulic lift works based on Pascal's principle, which states that when pressure is applied to a fluid in a confined space, the pressure is transmitted equally in all directions.

The pressure exerted by a liquid depends on its density, the depth of the liquid, and the acceleration due to gravity.

Note: The relationship between pressure, temperature, and molecules follows certain gas laws:

• Pressure is directly proportional to the temperature of the gas when volume is constant (Gay-Lussac's Law).
• Pressure is also directly proportional to the number of molecules when volume and temperature are constant (Avogadro's Law).
• While pressure is inversely proportional to volume, as per Boyle's Law, this does not apply to the direct relationship in question. 

A barometer is used to measure atmospheric pressure or the pressure of a gas.

When a person dives deep into a swimming pool, the pressure exerted by the water increases. This is because the depth of the water above the person increases, resulting in a greater weight of the water above and therefore higher pressure.

Pascal's principle states that the pressure in a fluid is transmitted equally in all directions.

The pressure exerted by a material depends on the force applied and the area over which the force is distributed. Since a block of iron is likely to have a higher force applied compared to other materials listed, it would exert the highest pressure.

A fully inflated balloon contains a higher pressure of gas compared to the surrounding air, making it an example of a high-pressure system.

According to the ideal gas law, increasing the temperature of a gas at constant volume will increase the pressure exerted by the gas.

According to Boyle's law, for a given amount of gas at a constant temperature, the pressure and volume are inversely proportional. Halving the volume while keeping the temperature constant will double the pressure, so it would be 4 atm.

The force applied can be calculated using the formula: force = pressure × area. Substituting the given values, we get force = 500 Pa × 2 m² = 1000 N.

In a fluid, pressure increases with increasing depth. This is due to the weight of the fluid above exerting a greater force at greater depths.

A low-pressure system refers to a situation where the air pressure is lower than surrounding areas.

• A deflated balloon is an example of a low-pressure system because it lacks the air pressure found in a fully inflated balloon or a tyre.
• In a deflated state, the air molecules are not compact, resulting in lower pressure inside compared to other options.

According to Boyle's law, when the volume of a gas is halved at constant temperature, the pressure doubles.

1 atm = 760 torr = 760 mm Hg One torr pressure is equivalent to 1 mm of mercury Pressure units equivalent to 1 atmosphere:

• 760 torr
• 760 mm Hg
• 76 cm Hg
• 101.325 kPa
• 1013 mbar