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.
A 8.1 %
B 8.5 %
C 48 %
D 83 %
Trains supply coal to a power station. The table below gives quantities describing the operation of the power station.
Which expression gives the efficiency of the power station?
A
B
C
D
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.
A 30 J
B 3.0 × 10^3 J
C 3.0 × 10^5 J
D 3.0 x 10^7 J
A transformer has the following input and output.
What is the efficiency of the transformer?
A 0.94 %
B 1.0 %
C 11 %
D 94 %
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?
The diagram shows the design of a water wheel which drives a generator to produce electrical energy. The flow rate of the water is 200 kg.s^–1. The generator supplies a current of 32 A at a voltage of 230 V.
Ignoring any changes in kinetic energy of the water, what is the efficiency of the system?
A 14 %
B 16 %
C 22 %
D 47 %
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