Question

Figure shows a block and tackle system of pulleys used to lift a load. What is the mechanical dvantage of the system?

Answer 1

Given:
The block and tackle system consists of 4 pulleys, i.e. $n=4$
In a n-pulley block and tackle system, if the effort is applied in the downward direction then the tension in the n segments of the string supports the load.
$L=nT\text{and}E=T$
So $E=\frac{L}{n}\Rightarrow E=\frac{L}{4}$
Hence, Mechanical advantage
$M.A.=\frac{loadL}{effortE}=\frac{nT}{T}=n=4$
Thus, the mechanical advantage is equal to the number of pulleys in both the blocks.