A railway engine accelerates a train of total mass 800 tonnes (1 tonne = 1000 kg) from rest to a speed of 50 m.s^–1.

How much work must be done on the train to reach this speed?

• A 1.0 × 10^6 J

• B 2.0 × 10^6 J

• C 1.0 × 10^9 J

• D 2.0 × 10^9 J

Water from a reservoir is fed to the turbine of a hydroelectric system at a rate of 500 kg.s^–1.
The reservoir is 300 m above the level of the turbine.
The electrical output from the generator driven by the turbine is 200 A at a potential difference of 6000 V.

What is the efficiency of the system?

• A 8.0 %

• B 8.2 %

• C 80 %

• D 82 %

A piston in a gas supply pump has an area of 500 cm2 and it moves a distance of 30 cm during one stroke.
The pump moves the gas against a fixed pressure of 4000 Pa.

How much work is done by the piston during one stroke?

• A 60 J

• B 6.0 × 10^3 J

• C 6.0 × 10^5 J

• D 6.0 × 10^7 J

A railway engine accelerates a train of total mass 1200 tonnes (1 tonne = 1000 kg) from rest to a speed of 75 m.s^–1.

How much useful work must be done on the train to reach this speed?

• A 1.7 × 10^6 J

• B 3.4 × 10^6 J

• C 1.7 × 10^9 J

• D 3.4 × 10^9 J

A crane is being used to lift containers off a ship. One container has a mass of 14 000 kg and is being lifted vertically with a speed of 3.2 m.s^–1.
The electric motor being used to supply the power to lift the container is using a current of 240 A at a potential difference of 2200 V.

What is the efficiency of the system?

• A 8.1 %

• B 8.5 %

• C 48 %

• D 83 %

A piston in a gas supply pump has an area of 400 cm2 and it moves a distance of 25 cm during one stroke.
The pump moves the gas against a fixed pressure of 3000 Pa.

How much work is done by the piston during one stroke?

• A 30 J

• B 3.0 × 10^3 J

• C 3.0 × 10^5 J

• D 3.0 x 10^7 J

The data below are taken from a test of a petrol engine for a motor car.
power output 150 kW
fuel consumption 20 litres per hour
energy content of fuel 40 MJ per litre

Which expression will evaluate the efficiency of the engine?