Two electric saws, P and Q, each operate for 20 s while cutting timber. Saw P does 3.0 kJ of useful work and saw Q does 2.0 kJ of useful work.
Which statement correctly compares the useful power outputs of the saws?
P has the greater useful power because it does more useful work in the same time.
P and Q have the same useful power because they operate for the same time.
Q has the greater useful power because it wastes less energy while cutting.
Their useful powers cannot be compared without knowing the total energy supplied.
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.