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?
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.