Physics Preliminary Examination 2023

The diagram shows a truck travelling down a slope. Where should the centre of gravity of the truck be, in order to have the lowest risk of toppling?

• A

• B

• C

• D

A force moves a block of wood up a slope at constant speed.

• A

• B

• C

• D

A stone is falling through the air. The acceleration of free fall is 10 m / s^2. Ignoring air resistance, what happens to the stone every second during its fall?

• The acceleration of the stone increases by 10 m / s^2.

• The speed of the stone increases by 10 m / s.

• The stone travels a distance of 10 m.

• The stone travels at a speed of 10 m / s

A car moves along a level road. The diagram shows all of the horizontal forces acting on the car. Which statement is correct?

• The car is slowing down.

• The car is speeding up.

• The car is moving at constant speed.

• The car is moving backwards.

What increases when a liquid becomes a gas at its boiling point?

• the average kinetic energy of the molecules

• the molecular size

• the molecular spacing

• the total number of molecules

A container is filled with 5 kg of paint. The density of the paint is 2 g / cm^3. Which volume of container is needed?

• 10 cm^3

• 400 cm^3

• 2500 cm^3

• 10 000 cm^3

A rectangular metal block measures 4.0 cm x 5.0 cm x 10 cm. The mass of the block is 0.8 kg. What is the pressure the box exerts on the floor as shown in the diagram?

• 0.016 N/cm^2

• 0.020 N/cm^2

• 0.16 N/cm^2

• 0.20 N/cm^2

Answer explanation

The pressure is calculated by dividing the weight by the area of contact. Pressure = Weight/Area = 0.8 kg x 10 N/kg / (5.0 cm x 10.0 cm) = 0.16 N/cm^2.

When a 300 N force is applied to a box weighing 600 N, the box moves 3.0 m horizontally in 20 s. What is the average power?

• 45 W

• 90 W

• 900 W

• 1800 W

Answer explanation

Average power is calculated by dividing work done by time taken. Work done is force multiplied by distance, then divided by time. (300 N * 3.0 m) / 20 s = 45 W.

• A

• B

• C

• D

In solids, thermal energy is transferred by conduction.

What is the cause of conduction?

• change in density

• expansion

• infra-red radiation

• molecular vibrations