The hoist, the motor of which is connected to a 120 V network, at a current of 4 A, evenly lifts a load weighing

The hoist, the motor of which is connected to a 120 V network, at a current of 4 A, evenly lifts a load weighing 72 kg. Determine the speed of lifting the load if the efficiency of the hoist is 75%.

Initial data: U (mains voltage) = 120 V; I (current) = 4 A; m (mass of evenly lifted load) = 72 kg; η (efficiency of the used lift) = 75% (0.75).

Constants: according to the condition g (gravitational acceleration) = 10 m / s2.

To determine the desired speed of lifting the load, we use the formula: η = Ap / Az = m * g * h / (U * I * t) = (m * g / (U * I) * (h / t) = (m * g / (U * I) * V, whence V = η * U * I / (m * g).

Let’s calculate: V = 0.75 * 120 * 4 / (72 * 10) = 0.5 m / s.