From a cellar 2 m deep, the boy took out a box weighing 6 kg. At the same time, he performed 1.2 kJ

From a cellar 2 m deep, the boy took out a box weighing 6 kg. At the same time, he performed 1.2 kJ of work. Find the boy’s efficiency.

h = 2 m.

g = 9.8 m / s2.

m = 6 kg.

Efficiency -?

Azat = 1.2 kJ = 1200 J.

Coefficient of efficiency The efficiency shows in percentage what part of the spent work Azat goes into useful Apol.

Efficiency = Apol * 100% / Azat.

Let us express the useful work of the boy Apol by the formula: Apol = m * g * h, where m is the mass of the load that the boy lifted, g is the acceleration of free fall, h is the height to which the boy lifted the load, that is, the depth of the cellar.

Efficiency = m * g * h * 100% / Azat.

Efficiency = 6 kg * 9.8 m / s2 * 2 m * 100% / 1200 J = 9.8%.

Answer: the boy performed work with an efficiency of 9.8%.