Question

The $\mathrm{MA}$ of a machine is $5$ and its efficiency is $80\%$. It is used to lift a load of $200\mathrm{kgf}$ to a height of $20\mathrm{m}$. What is the effort required?

• A. $10\mathrm{kgf}$
• B. $20\mathrm{kgf}$
• C. $40\mathrm{kgf}$
• D. $50\mathrm{kgf}$

Answer 1

The correct option is C

$40\mathrm{kgf}$

Step 1: Given data.

The mechanical advantage of machine is $\left(\mathrm{MA}\right)=5$

The efficiency of the machine is $\eta =80\%$

Load is $\mathrm{P}=200\mathrm{kgf}$

The height up to which it was raised is $\mathrm{h}=20\mathrm{m}$

Step 2: Find the effort required,

The mechanical advantage in terms of the load and effort is,

$\left(\mathrm{MA}\right)=\frac{\mathrm{Load}}{\mathrm{Effort}}$

Substitute the given values in the mechanical advantage formula

$\begin{array}{rcl}5& =& \frac{200\mathrm{kgf}}{\mathrm{Effort}}\\ \mathrm{Effort}& =& \frac{200}{5}\\ & =& 40\mathrm{kgf}\end{array}$

So, the effort required is $40\mathrm{kgf}$.

Therefore, the correct option is (C).