The 2.4 kW motor of the crane lifts the load at a speed of 4.2 m / min.

The 2.4 kW motor of the crane lifts the load at a speed of 4.2 m / min. determine the weight of the lifted load, if the efficiency of the crane is 82%.

Initial data: Ns (power of the crane motor) = 2.4 kW = 2400 W; V (lifting speed) = 4.2 m / min; η (efficiency of the crane motor) = 82% = 0.82.

Reference data: g (acceleration due to gravity) = 10 m / s ^ 2.

SI system: V = 4.2 m / min = 4.2 / 60 m / s = 0.07 m / s.

The efficiency of the crane motor can be represented by the formula: η = Np / Nz = F * V / Nz = P * V / Nz, whence P = Nz * η / V.

Let’s perform the calculation: P = 2400 * 0.82 / 0.07 = 28 114 N ≈ 28.1 kN.

Answer: The weight of the load being lifted is 28.1 kN.