Unit 2 - Density and Pressure

What is the unit of density?

• Grams per litre (g/L)

• Newtons (N)

• Kilograms per metre cubed (kg/m³)

• Pascals (Pa)

Answer explanation

The unit of density is kilograms per metre cubed (kg/m³), which measures mass per unit volume. Grams per litre (g/L) is also a valid unit but less common in scientific contexts. The other options (N and Pa) measure force and pressure, respectively.

How is density calculated?

• Density = Force / Area

• Density = Mass x Volume

• Density = Mass / Volume

• Density = Volume / Mass

Answer explanation

Density is calculated using the formula Density = Mass / Volume. This means that density is the ratio of an object's mass to its volume, making the correct choice the third option.

What is the first step to find the density of a liquid?

• Tare the balance

• Calculate the density using the formula

• Measure the mass of the measuring cylinder

• Measure the volume of the liquid

Answer explanation

The first step to find the density of a liquid is to measure the mass of the measuring cylinder. This allows you to determine the mass of the liquid alone after adding it, which is essential for calculating density.

What is parallax error?

• Error in measuring mass

• Error in reading volume due to angle

• Error in calculating density

• Error in measuring pressure

Answer explanation

Parallax error occurs when the measurement of volume is affected by the angle of observation. This can lead to inaccurate readings, making 'Error in reading volume due to angle' the correct choice.

How do you find the volume of an irregularly shaped solid?

• Use a ruler to measure dimensions

• Weigh it on a balance

• Immerse it in water and measure displaced volume

• Use a mathematical formula

Answer explanation

To find the volume of an irregularly shaped solid, immerse it in water. The volume of water displaced equals the volume of the solid, making this method effective for irregular shapes.

What is pressure defined as?

• Mass per unit volume

• Volume per unit area

• Force per unit area

• Weight per unit volume

Answer explanation

Pressure is defined as force applied per unit area. This means that the correct choice is 'Force per unit area', as it accurately describes how pressure is calculated and understood in physics.

What happens to pressure as depth increases in a fluid?

• It fluctuates

• It increases

• It remains constant

• It decreases

Answer explanation

As depth increases in a fluid, the weight of the fluid above exerts more force, leading to an increase in pressure. Therefore, the correct answer is that pressure increases with depth.

What is the formula for pressure in a fluid?

• p = m/V

• p = A/F

• p = F/A

• p = ρgh

Answer explanation

The correct formula for pressure in a fluid is p = ρgh, where ρ is the fluid density, g is the acceleration due to gravity, and h is the height of the fluid column. This formula reflects how pressure increases with depth in a fluid.

What does the pressure at a point in a gas or liquid at rest do?

• Acts in one direction

• Acts equally in all directions

• Acts only upwards

• Acts only downwards

Answer explanation

In a gas or liquid at rest, pressure acts equally in all directions due to the random motion of particles. This isotropic nature of pressure ensures that it is transmitted uniformly, making 'acts equally in all directions' the correct choice.

What is the effect of gravitational field strength on pressure?

• It only affects solids

• It has no effect

• It increases pressure

• It decreases pressure

Answer explanation

Gravitational field strength increases the weight of an object, which in turn increases the pressure it exerts on the surface below. Therefore, the correct answer is that it increases pressure.