Question

A block and tackle system has $5$ pulleys. If an effort of $1000N$ is needed in the downward direction to raise a load of $4500N$. Calculate the efficiency of the system.

• A. $80\%$
• B. $90\%$
• C. $50\%$
• D. $60\%$

Answer 1

Answer: (B)

$90\%$

As we know that efficiency ($\eta$) =$\frac{mechanicaladvantage}{velocityratio}$

Mechanical Advantage(M.A) =$\frac{load}{effort}$=$\frac{4500}{1000}$ = 4.5

Velocity Ratio(V.R) = No. of pulleys used = 5

Therefore efficiency $\eta$ =$\frac{4.5}{5}$$\times$100% = 90%