Question

A system of pulleys is used to lift a load of $500kgwt$ If the velocity ratio and MA are $0.9and5$ then the efficiency and effort required to lift the load are

• A. $5.6$,${10}^{8}N$
• B. $5.6,{10}^{8}dyne$
• C. $2.6,{10}^{7}N$
• D. $2.6,{10}^{7}dyne$

Answer 1

The correct option is B

$5.6,{10}^{8}dyne$

Step 1: Given data

Load =$500kgwt$

velocity ratio =$0.9$

Mechanical advantage =$5$

Step 2: Calculations

Efficiency is given by the equation,

$Efficiency=\frac{Mechanicaladvantage}{velocityratio}$

Substituting,

$Efficiency=\frac{5}{0.9}=5.6$

So,

$$\begin{gathered} effortrequired=\frac{Load}{Mechanicaladvantage}=\frac{mg}{MA} \\ Effort=\frac{500\times 10}{5}=1000N \end{gathered}$$

Converting the value to dyne,

$1000N=1000\times {10}^{5}dyne={10}^3\times {10}^5={10}^{8}dyne$

Hence, option (b) is correct