Box with nails weighing 54 kg. with the help of a movable block, they are raised to the 5th floor.

Box with nails weighing 54 kg. with the help of a movable block, they are raised to the 5th floor. With what force does the worker pull the box at efficiency = 75%

Data: m (weight of the box with nails) = 54 kg; η (efficiency of the used mechanism) = 75% (0.75); the box with nails is lifted with the help of a movable block (the gain in strength is 2 times).

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

The force with which the worker pulls the box can be calculated using the formula for calculating the efficiency: η = Apol. / Azatr. = ΔЕп / (F * L) = m * g * h / (F * 2h) = m * g / 2F, whence F = m * g / 2η.

Calculation: F = 54 * 10 / (2 * 0.75) = 360 N.

Answer: The worker pulls the box with a force of 360 N.