# The crane evenly lifts a load weighing 2 tons. The net power of the crane is 4.4 kW. What is the speed of lifting the load?

m = 2 t = 2000 kg.

g = 10 m / s2.

Np = 4.4 kW = 4400 W.

V -?

The useful power of the crane Np is expressed by the formula: Np = Ap / t, where Ap is the useful work of the crane, t is the work time.

The useful work of the crane Ap is expressed by the formula: Ap = F * h.

Since I lift the load evenly, according to 1 Newton’s law, the force F with which the crane acts on the load is equal to the gravity of the load m * g: F = m * g.

Nп = m * g * h / t = m * g * V, since the ratio of the height h to the time of lifting the load t is the speed of its lifting V: V = h / t.

V = Nп / m * g.

V = 4400 W / 2000 kg * 10 m / s2 = 0.22 m / s.

Answer: the crane lifts the load at a speed of V = 0.22 m / s.

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