Quiz on Pressure

Which statement correctly defines pressure?

• Pressure is the amount of work done per unit time.

• Pressure is the force exerted by a body, multiplied by its area.

• Pressure is the gravitational force exerted on a body.

• Pressure is the force acting per unit area.

Answer explanation

Pressure is defined as the force acting per unit area, which means it quantifies how much force is applied over a specific area. This makes the statement 'Pressure is the force acting per unit area' the correct definition.

A lady of mass 64.0 kg wears high heels. The total area of her high heels in contact with the ground is 0.0200 m^2. If the gravitational field strength g is 10.0 N/kg, how much pressure does she exert on the ground?

• 3200 N/m^2

• 32000 N/m^2

• 12.8 N/m^2

• 1280 N/m^2

Answer explanation

To find the pressure, use the formula: Pressure = Force / Area. The force is the weight of the lady, which is mass × g = 64.0 kg × 10.0 N/kg = 640 N. Thus, Pressure = 640 N / 0.0200 m² = 32000 N/m².

A hydraulic press uses an enclosed liquid to transmit pressure. What are two key principles that allow a hydraulic press to lift heavy loads with a small amount of force?

• Liquids are compressible, and pressure is inversely proportional to the area.

• Liquids are incompressible, and pressure applied to an enclosed liquid is transmitted equally to all parts of the liquid.

• The force exerted is directly proportional to the distance moved, and energy is not conserved.

• The area of contact is maximized, and the force is applied directly to the load.

Answer explanation

Hydraulic presses rely on the fact that liquids are incompressible, allowing pressure to be transmitted equally throughout the liquid. This principle enables a small force to lift heavy loads effectively.

A liquid has a mass of 500 kg and occupies a volume of 0.50 m^3. What is the density of the liquid?

• 0.00100 kg/m^3

• 250 kg/m^3

• 1000 kg/m^3

• 2500 kg/m^3

Answer explanation

Density is calculated as mass divided by volume. Here, density = 500 kg / 0.50 m^3 = 1000 kg/m^3. Thus, the correct answer is 1000 kg/m^3.

A point is located at a depth of 0.090 m in a test-tube filled with water. Given that the density of water is 1000 kg/m^3 and the gravitational field strength is 10 N/kg, what is the pressure at this point due to the water column?

• 90 Pa

• 900 Pa

• 9000 Pa

• 90000 Pa

Answer explanation

Pressure is calculated using the formula P = h * ρ * g, where h = 0.090 m, ρ = 1000 kg/m³, and g = 10 N/kg. Thus, P = 0.090 * 1000 * 10 = 900 Pa. Therefore, the correct answer is 900 Pa.

Which of the following statements about atmospheric pressure is correct?

• Atmospheric pressure acts only downwards.

• Atmospheric pressure is not affected by the density of the atmosphere.

• Atmospheric pressure acts equally in all directions.

• Atmospheric pressure is only present in a vacuum.

Answer explanation

Atmospheric pressure acts equally in all directions due to the random motion of air molecules. This means it exerts force not just downwards, but also upwards and sideways, making the correct statement about atmospheric pressure.

How is the height of a liquid column in a barometer used to measure atmospheric pressure?

• The height of the liquid column is directly proportional to the density of the liquid, which determines atmospheric pressure.

• The height of the liquid column is inversely proportional to the atmospheric pressure, meaning a higher column indicates lower pressure.

• The height of the liquid column directly corresponds to the surrounding atmospheric pressure, as they are in equilibrium.

• The height of the liquid column is only affected by the shape and size of the barometer tube, not atmospheric pressure.

Answer explanation

The height of the liquid column in a barometer reflects the surrounding atmospheric pressure. When atmospheric pressure increases, it pushes the liquid higher, establishing an equilibrium that directly corresponds to the pressure.

The height of the mercury column in a simple mercury barometer is 76 cm. If the density of mercury is 13600 kg/m^3 and the gravitational field strength (g) is 10 N/kg, what is the atmospheric pressure?

• 1.03 kPa

• 10.3 kPa

• 103 kPa

• 1030 kPa

Answer explanation

To find atmospheric pressure, use the formula: Pressure = height × density × g. Here, Pressure = 0.76 m × 13600 kg/m³ × 10 N/kg = 103 kPa. Thus, the correct answer is 103 kPa.

Which of the following principles is most directly applied when using a manometer to measure the pressure difference between two gases?

• The principle that gases are highly compressible, allowing for volume changes.

• The fact that atmospheric pressure acts equally in all directions.

• The principle that for a liquid at rest, the pressure is the same at all points along the same horizontal level.

• The relationship between pressure, force, and area (Pressure = Force / Area).

Answer explanation

The correct choice highlights that in a manometer, the pressure at the same horizontal level in a liquid is equal, allowing for accurate measurement of pressure differences between gases.

The diagram shows a manometer used to measure the pressure difference between Gas X and Gas Y. The difference in the height of the mercury columns is 3.0 cm. Given that the density of liquid used in the manometer is 6000 kg/m^3 and the gravitational field strength is 10 N/kg, what is the pressure difference between Gas X and Gas Y?

• 0 Pa

• 1.8 kPa

• 18 kPa

• 180 kPa

Answer explanation

The pressure difference can be calculated using the formula: P = h x ρ x g. Here, h = 0.030 m, ρ = 6000 kg/m³, and g = 10 N/kg. Thus, P = 0.030 x 6000 x 10 = 1800 Pa or 1.8 kPa.