# If you apply a force of 50 N, a pulley system can lift a box with a mass of 20 kg. What is the mechanical advantage of the pulley system?

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justaguide | College Teacher | (Level 2) Distinguished Educator

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The mechanical advantage is the ratio of the output force and that of the input force. Machines are used with a mechanical advantage greater than 1 as it is easier to apply a small force over a prolonged displacement rather than a very large force over a small distance. It should be noted that the output energy cannot be larger than the input energy.

Here, a pulley is used to apply a force of 50 N which allows a mass of 20 kg to be lifted. The mass of the box is 20 kg and there is a gravitational force acting on it that accelerates it downwards with an acceleration equal to 9.8 m/s^2

The weight of the box is 20*9.8 = 196 N

The mechanical advantage here is 196/50 = 3.92.

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