Question

A block and tackle system has $\mathrm{VR}=5$.
(i) Draw a neat labeled diagram of a system indicating the direction of its load and effort.
(ii) Rohan exerts a pull of $150\mathrm{kgf}$. What is the maximum load he can raise with this pulley system if its efficiency is $75\%$ ?

Answer 1

Step 1: (i) Diagram indicating the direction of its load and effort,

1. A neat labeled diagram of a system indicating the direction of its load and effort.
2. In the given diagram effort is represented by $\mathrm{S}$ and load is represented by $\mathrm{F}$.

Step 2: (ii) Given data,

Effort $\left(E\right)=150\mathrm{kgf}$

Efficiency $\left(\eta \right)=75\%$

Velocity ratio $\left(VR\right)=5$

Step 3: Find the mechanical advantage $\left(MA\right)$,

We know that $\left(\eta =\frac{MA}{VR}\times 100\right)$

Substitute the values in the above formula.

$$\begin{gathered} 75=\frac{MA}{5}\times 100 \\ MA=3.75 \end{gathered}$$

Step 4: Find the load.

We know that $\left(MA=\frac{\mathrm{Load}\left(L\right)}{\mathrm{Effort}\left(E\right)}\right)$.

Substitute the values in the above formula.

$\begin{array}{rcl}3.75& =& \frac{L}{150\mathrm{kgf}}\\ L& =& 150\times 3.75\\ & =& 562.5\mathrm{kgf}\end{array}$

Thus, the maximum load Rahul can raise with this pulley system is $562.5\mathrm{kgf}$.