Question

A block and tackle system has $5$ pulleys. If an effort of $1000\text{N}$ is needed in the downward direction to raise a load of $4500\text{N}$, calculate the efficiency($\%$) of the system.

• A. 90

Answer 1

The correct option is A 90
Given,
Number of pulleys, $\text{n}=5$
Effort = $1000\text{N}$
Load = $4500\text{N}$

Mechanical advantage, M.A$=\frac{\text{Load}}{\text{Effort}}=\frac{4500}{1000}=4.5$

As we know velocity ratio = $\text{n}$
$\therefore$ Efficiency, $\eta =\frac{\text{M.A.}}{\text{V.R.}}=\frac{4.5}{5}=0.9=90\%$