Mechanical Advantage

Imagine you are trying to pry open a heavy lid with a spoon. The spoon makes you feel stronger, right? This 'strength boost' is what scientists call Mechanical Advantage (MA). It is a measure of how much a machine multiplies the force you put into it. If a machine has a mechanical advantage of $2$, it doubles your force. If it has a mechanical advantage of $10$, it makes you ten times stronger! We call the force you apply the Input Force ($F_{in}$) and the force the machine exerts on the object the Output Force ($F_{out}$).

To find the exact mechanical advantage of any machine, we use a simple ratio. We divide the Output Force by the Input Force. The formula looks like this:

One interesting thing to notice is that Mechanical Advantage has no units. Because you are dividing Newtons by Newtons, the units cancel out, leaving you with a pure number that tells you the 'magnification' level of the machine.

You might wonder: 'If machines make me stronger, why don't we use them for everything?' The answer is the Trade-Off. You never get something for nothing in physics. If a machine multiplies your force, you have to move a longer distance to make up for it. For example, to lift a heavy box $1$ meter using a ramp, you might have to push it $5$ meters along the ramp's surface. You use less force, but you use it over a much longer path!

A machine can never do more Work than you put into it. In fact, because of friction, the output work is always a little bit less than the input work. Friction turns some of your effort into heat energy. This is why we can't create a 'perpetual motion machine.' The Work Output ($F_{out} \times d_{out}$) will never exceed the Work Input ($F_{in} \times d_{in}$). Machines don't create energy; they just change how we use it.