A crane with a 6 kW motor evenly lifts a load of 5 kg. How fast does the crane lift the load?

Np = 6 kW = 6000 W.

m = 5 kg.

g = 10 m / s2.

V -?

The useful power of the crane Np will be determined by the formula: Np = Ap / t, where Ap is the useful work that the crane performs when the body is lifted, t is the work time.

The useful work of the crane Ap is to lift a body of mass m to a height h: Ap = m * g * h, where g is the acceleration of gravity.

Since the body is lifted uniformly, the ratio of the height h to the time of lifting the load t will be the speed of lifting the load V: V = h / t.

The formula for determining the net power Np of the crane will take the form:

Nп = m * g * h / t = m * g * V.

V = Nп / m * g.

V = 6000 W / 5 kg * 10 m / s2 = 120 m / s.

Answer: the crane lifts the load at a speed of V = 120 m / s.