What work needs to be done to lift a 50 kg load to a height of 13 m using a fixed block?

What work needs to be done to lift a 50 kg load to a height of 13 m using a fixed block? The efficiency of this simple mechanism is 93%.

m = 50 kg.

g = 9.8 m / s2.

h = 13 m.

Efficiency = 93%.

Azat -?

Let us write down the definitions for the efficiency: efficiency = Apol * 100% / Azat, where Azat is the work to be done, Apol is useful work.

We find Apol’s useful work by the formula: Apol = m * g * h, where m is the mass of the body that was lifted, g is the acceleration of gravity, h is the height of the body.

Let us express the work expended: Azat = Apol * 100% / efficiency.

Azat = 50 kg * 9.8 m / s2 * 13 m * 100% / 93% = 6849 J.

Answer: to lift the load, you need to do the work Azat = 6849 J.