Question

Why is the mechanical advantage of a second class lever always greater than 1, whereas that of a third class lever is always less than 1?

Answer 1

The mechanical advantage of a second-class lever is always greater than 1:

1. We know, the effort arm is always longer than the load arm.
2. In Class II levers, the fulcrum and the effort are at the two ends of the lever and the load is somewhere in between the effort and the fulcrum.
3. $Mechanicaladvantage\left(MA\right)=\frac{Effortarm}{Loadarm}$
4. Since, the effort arm is always longer than the load arm.
5. From the equation above, it is clear that the MA of the Class II levers is always greater than 1.
6. In other words a second-class lever always acts as a force multiplier is less effort is needed to overcome a large load.

The mechanical advantage of a third-class lever is always less than 1:

1. In these types of levers, the effort is in between the fulcrum F and the load L.
2. Thus, the effort arm is always smaller than the load arm.
3. This helps by reducing the applied force(effort).
4. So, it is a speed multiplier.
5. $Mechanicaladvantage\left(MA\right)=\frac{Effortarm}{Loadarm}$
6. From the equation above, it is clear that the MA of the Class III levers is always less than 1.

Hence, the mechanical advantage of a second-class lever is always greater than 1, whereas that of a third-class lever is always less than 1.