Chapter 7 - Pressure

What is pressure ?

• product of mass and acceleration

• force per unit volume

• force per unit area

• product of force and area

To prevent a cement mixer from sinking into soft ground, the mixer is placed on a large flat board.           

Why does this prevent the mixer from sinking?

• The large area increases the pressure on the ground.

• The large area increases the weight on the ground.

• The large area decreases the pressure on the ground.

• The large area decreases the weight on the ground.

The pressure of a gas is measured using a manometer as shown in the diagram. 

The mercury in the manometer is replaced with a liquid which is less dense.  How does the value of h change?

• It becomes 0

• It decreases, but not to 0

• It stays the same

• It increases

Pressure is defined as ...

• the product of the height of a liquid column, the density of the liquid and the gravitational field strength.

• the product of applied force and cross-sectional area.

• the ratio of the applied force to the area over which the force is applied.

• the ratio of the applied force to the parallel distance moved by the force.

Determine the pressure exerted by the cylinder in the following diagram. The volume of the cylinder is given by π × r² × L, where r is the radius of the cylinder and L is its length. It is also given that its density is ρ and that the gravitational field strength is g.

• ρ × L × g

• π × r² × L × ρ × g

Choose the most appropriate explanation for the statement, “Compared to wearing high-heeled shoes, wearing a pair of sports shoes will help to reduce the pressure on your soles.”

• A smaller impact force is exerted by the ground on the soles.

• A larger contact area between the soles and the ground is provided.

• The force of the soles on the ground is reduced.

• The friction between the shoes and the ground is increased.

Determine the contact area of a book resting on a table, if the weight of the book is 8.00 N and the pressure exerted on the table by the book is 50.0 Pa.

• 6.25 cm²

• 160 cm²

• 400 cm²

• 1600 cm²

Arrange the positions in the container in order of increasing pressure.

• A, D, B, E, C

• A, B, D, C, E

• B, A, D, C, E

• A, D, E, B, C

In a container, a layer of oil floats on a layer of water, as shown below. Oil has a lower density than water. Which of the following graphs correctly shows the variation of pressure with depth?

• A

• B

• C

• D

Calculate the pressure experienced by a diver 50 m underwater. You may assume that the density of seawater is 1000 kg m⁻³, the gravitational field strength is 10 N kg⁻¹ and the atmospheric pressure at sea level is 1.01 × 10⁵ Pa. 

• 1.51 × 10⁵ Pa

• 3.99 × 10⁵ Pa

• 5.00 × 10⁵ Pa

• 6.01 × 10⁵ Pa