Pressure (Cambridge O Level Physics)

Fig.5.1 shows a glass bottle containing air. The bottle is sealed with a cap.

The air in the bottle becomes warmer.

The bottle has a weight of 5.4 N and an area of 9.2 cm² in contact with the table.

 
Calculate the pressure produced by the bottle on the table. Give the unit.

pressure = ......................................................... 

Fig. 5.2 shows another bottle. The bottle is on a table. Part of the base of this bottle is not in contact with the table.

 

Fig. 4.1 shows a pin. Fig. 4.2 shows a person pushing the pin into a wall.

The area of the top surface of the pin is 1.8 cm².

The person applies a force of 50 N.

Calculate the pressure exerted on the top surface of the pin.      

pressure = ............................................. N / cm² 

The area of the top surface of the pin is 500 times larger than the area of the point.

Calculate the value of the pressure exerted by the point on the wall.      

Fig 2.1 shows liquid in a cylinder.

Table 2.1 gives some data about the cylinder and the liquid.

The cylinder containing liquid is placed on a digital balance that displays the mass in kg.

 
Calculate the reading shown on the balance.

Fig. 2.2 shows a device called a manometer that measures the pressure of a gas.

On a particular day, the atmospheric pressure is 1.0 × 10⁵ Pa. A bubble of gas forms at a point 5.0 m below the surface of a lake. The density of water is 1000 kg/m³.

Determine

As the bubble rises to the surface, the mass of gas in the bubble stays constant. The temperature of the water in the lake is the same throughout.

Explain why the bubble rises to the surface and why its volume increases as it rises.

Fig. 3.1 shows an archer pulling the string of a bow.

The archer uses a force of 120 N. The force acts on an area of 0.5 cm² on the archer’s fingers.

Calculate the pressure on the archer’s fingers.

pressure on fingers = ............................................ N/cm² 

The archer’s other hand is pushing the bow with the same force of 120 N. This force acts on a larger area than the force in (a).

State whether the pressure on this hand is greater than, the same as or less than the pressure on the fingers holding the string.

State the energy store of the bow that energy is transferred into when the archer bends it as shown in Fig. 3.1.

Fig. 4.1 shows liquid in a cylinder.

The depth of the liquid is 10 cm and the radius of the cylinder is 3.0 cm. The weight of the liquid in the cylinder is 2.5 N.

 
Calculate the density of the liquid. You can assume that acceleration of free fall is 10 m/s².

density = ...........................................................

Fig. 4.2 shows a device called a manometer that measures the pressure of a gas supply.

A rectangular container has a base of dimensions 0.12 m × 0.16 m. The container is filled with a liquid. The mass of the liquid in the container is 4.8 kg.

Calculate

Explain why the total pressure on the base of the container is greater than the value calculated in (a)(ii).

The depth of liquid in the container is 0.32 m.

Calculate the density of the liquid.

density = ...........................................................

A scientist fills a container with seawater. The container has dimensions 30 cm × 30 cm × 40 cm. The density of seawater is 1020 kg/m³.

Calculate the mass of the seawater in the container.

mass = .........................................................

Fig. 2.1 shows a submarine. The submarine is fully submerged in the sea.

Fig. 2.1 shows a hollow metal cylinder containing air, floating in the sea.

The density of the metal used to make the cylinder is greater than the density of seawater.

Explain why the cylinder floats.

The cylinder has a length of 1.8 m. It floats with 1.2 m submerged in the sea. The bottom of the cylinder has an area of cross-section of 0.80 m².

 
The density of seawater is 1020 kg/m³. Calculate the force exerted on the bottom of the cylinder due to the depth of the seawater.

force = ...........................................................

Deduce the weight of the cylinder. Explain your answer.

A cylindrical container has a base with diameter of 0.15 m and is filled with water to a depth of 0.35 m as shown in Fig. 1.1.

The mass of the water is 6.2 kg.

Calculate the weight of the water in the container.

Calculate the pressure due to the liquid on the base of the container.

The water-filled cylinder is placed on a laboratory bench.

Suggest reasons why the total pressure on the bench is higher than the value calculated in part (b).

A bead of hollow glass is dropped into the water and comes to rest floating 12 cm above the base of the cylinder as shown in Fig. 1.2.

Calculate the total pressure on the bead.