# A crane A lifts a heavy load in 5 seconds, whereas another crane B

Force, Work, Power & Energy (10)
A crane ‘A’ lifts a heavy load in 5 seconds, whereas another crane ‘B’ does the same work in 2 seconds. Compare the power of crane ‘A’ to that of crane ‘B’.

### Answer

P_{A}/ P_{B} = W_{A} / t_{A} ÷ W_{B} / t_{B}

∴ P_{A} /P_{B} = W_{A} /t_{A} × t_{B} / W_{B}

but W_{A} = W_{B} ∴ P_{A} / P_{B} = t_{B} / t_{A}

∴ P_{A}: P_{B} = 2: 5