What factors affect the mechanical advantage of a lever?
If on one end of a class 1 lever in equilibrium force
Consider a lever of the 1st class that consists of a rigid rod that can rotate around a fulcrum. When one end of a rod goes up, another goes down.
This lever can be used to lift up a heavy object with significantly weaker than its weight force. It all depends on the lengths of points of application of forces from the fulcrum of the lever.
Assume that a heavy load is positioned at a length
On the opposite side of a rod at a distance
The fact that a lever is in equilibrium means that the work performed by forces
Rigidity of a rod that serves as a lever means that the angle a lever turns around a fulcrum is the same on both ends of a lever.
Assume that a lever turned by a small angle
On the other end of a rod, on distance
Both works must be the same, so
From the last formula we derive that the advantage of using a lever depends on a ratio between lever ends' distance from fulcrum. The more the ratio is - the more advantage we have and more weight we can lift.