A load weighing 450 kg is lifted using a movable block. What force must be applied

| August 11, 2021 | education

A load weighing 450 kg is lifted using a movable block. What force must be applied to the free end of the rope if the efficiency of the block is 80%

m = 450 kg.

g = 10 m / s2.

Efficiency = 80%.

F -?

Efficiency coefficient The efficiency of a simple mechanism shows what part of the spent work Az, expressed as a percentage, goes into the useful Ap: Efficiency = Ap * 100% / Az.

We will express the useful work Ap by the formula: Ap = m * g * h, where h is the height to which the load was lifted.

The expended work Az is expressed by the formula: Az = F * L, where L is the length of the rope for which they pulled.

For the movable block L = 2 * h.

Efficiency = m * g * h * 100% / F * 2 * h = m * g * 100% / F * 2.

F = m * g * 100% / 2 * efficiency.

F = 450 kg * 10 m / s2 * 100% / 2 * 80% = 2812.5 N.

Answer: to lift the load, it is necessary to apply a force F = 2812.5 N. to the free end of the rope.



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