An electric motor winds up the driving weight of a tower clock. The motor has a mean input power of 200 W and an efficiency of 0.75. It raises the 30 kg driving weight through a vertical height of 3.0 m at a steady speed.
Gravitational field strength is 10 N/kg.
How long does the motor take to raise the weight?
6.0 s6.0\ \mathrm{s}6.0 s
8.0 s8.0\ \mathrm{s}8.0 s
4.5 s4.5\ \mathrm{s}4.5 s
3.4 s3.4\ \mathrm{s}3.4 s
128 exam-style questions on Edexcel GCSE Physics 8.3 Power and efficiency, covering 8.3.1 Power and 8.3.2 Efficiency. Each one has a worked solution and a mark scheme showing where the marks go.