A crane is used to lift a heavy cargo container through a vertical distance of 5.0 m at a constant speed.
The operator increases the input power to the electric motor of the crane and lifts the same container through the same distance. The efficiency of the motor remains the same.
Which row in the table correctly describes the effect of this change on the useful work done lifting the container and on the time taken to lift it?
| Useful work done | Time taken | |
|---|---|---|
| A | decreases | decreases |
| B | stays the same | decreases |
| C | decreases | stays the same |
| D | stays the same | stays the same |
Useful work done: decreases; Time taken: decreases
Useful work done: stays the same; Time taken: decreases
Useful work done: decreases; Time taken: stays the same
Useful work done: stays the same; Time taken: stays the same
533 exam-style questions on CIE IGCSE Physics 1.7 Energy, work and power, covering 1.7.1a Energy stores and energy transfers, 1.7.1b Conservation of energy, 1.7.1c Kinetic and gravitational potential energy, 1.7.2 Work done, 1.7.3 Energy resources, 1.7.3a Energy resources and electricity generation, 1.7.3b Nuclear fusion as an energy source, 1.7.3c Efficiency of energy transfer, and 1.7.4 Power. Each one has a worked solution and a mark scheme showing where the marks go.