Question

Which one of the following options gives the mechanical advantages (MA) of a lever of the third-order?

• A. MA is always equal to 1
• B. MA is always greater than 1
• C. MA is always less than 1

Answer 1

The correct option is C

MA is always less than 1

1. According to the principle of a lever, we know
   $$\begin{gathered} Load\times Loadarm=Effort\times Effortarm \\ \Rightarrow \frac{Load}{Effort}=\frac{Effortarm}{Loadarm}----Equation\left(I\right) \\ SinceMA(mechanicaladvantage)=\frac{Load}{Effort} \\ Thereforeequation\left(I\right)becomes- \\ MA=\frac{Effortarm}{Loadarm} \end{gathered}$$
2. In a Class Three Lever, the Force is between the Load and the Fulcrum, and the effort arm is shorter than the load arm.
3. Therefore for class three lever, MA is always less than 1.
4. For example, a spade is a class three lever.
5. Hence option C is the correct answer.