# The power of the crane motor is 4.5 kW. How much weight can be lifted with this crane

October 4, 2021 | education

| **The power of the crane motor is 4.5 kW. How much weight can be lifted with this crane to a height of 12 m in 0.5 minutes. The engine efficiency is 80%.**

These tasks: Ns (crane motor power, consumed power) = 4.5 kW (4.5 * 103 W); h (height to which the load must be lifted) = 12 m; t (duration of the crane operation) = 0.5 min (30 s); η (motor efficiency) = 80%.

Reference values: g (acceleration due to gravity) ≈ 10 m / s2.

We express the maximum cargo mass from the formula: η = Np / Nz = (A / t) / Nz = ΔEp / (t * Nz) = m * g * h / (t * Nz), whence m = η * t * Nz / (g * h).

Calculation: m = 0.8 * 30 * 4.5 * 103 / (10 * 12) = 900 kg.

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