The crane performs work of 30 kJ, lifting the concrete slab to a height

The crane performs work of 30 kJ, lifting the concrete slab to a height of 20 m. How long does it take for a crane if it develops an average power of 1000W?

Given: A (perfect work when lifting a concrete slab) = 30 kJ (30 * 10 ^ 3 J); h (lifting height of the slab) = 20 m; N (average power developed by the crane used) = 1000 W.

The time it took for the crane used to lift the concrete slab can be expressed from the formula: N = A / t, whence t = A / N.

Let’s make a calculation: t = 30 * 10 ^ 3/1000 = 30 s.

Answer: The crane used took 30 seconds to lift the concrete slab.