Question

What is the mechanical advantage of a lever with an input arm of 5 m and an output arm of .5 m?

Answer 1

The lever arm is longer and therefore there is more torque.
tau = r X F = rF sin theta.
The longer the lever arm is, the less force you need to exert when turning something.
For example a wrench, the longer the wrench, the easier it is to turn whatever you're turning.