# The crane motor has a power of 3.2 kW. It can lift the load evenly at a speed of 4.8 m / s.

May 29, 2021 | education

| **The crane motor has a power of 3.2 kW. It can lift the load evenly at a speed of 4.8 m / s. The efficiency of the crane is 78%. What is the largest load in terms of mass that the crane can lift under these conditions?**

Efficiency: η = N1 / N2 * 100%, where η is the efficiency of the crane motor (η = 78% = 0.78), N1 is the net engine power (N1 = F * V, where F is the acting force (F = Ft = m * g, where m is the mass of the lifted load, g is the acceleration of gravity (we assume g = 10 m / s2), V is the speed of lifting the load (V = 4.8 m / s)), N2 is the power expended (N2 = 3.2 kW = 3.2 * 10 ^ 3 W).

η = m * g * V / N ^ 2 * 100%.

m = N ^ 2 * η / (g * V) = 3.2 * 10 ^ 3 * 0.78 / (10 * 4.8) = 52 kg.

Answer: The maximum load is 52 kg.

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