Question

A boy lifts a load of 400 N through a height of 5 m by a single fixed pulley. The effort applied at the other end is 480 N. The efficiency is.

• A. 86.6 %
• B. 72.5 %
• C. 83.3 %
• D. 75 %

Answer 1

The correct option is C 83.3 %

Given:
Load = $400\text{N}$
Effort = $480\text{N}$
Distance moved by effort end = Distance moved by load end = $5\text{m}$
Velocity Ratio (V.R) $=\frac{\text{Distance moved by effort}}{\text{Distance moved by load}}=\frac{5}{5}=1$

Mechanical advantage (M.A.) $=\frac{\text{Load}}{\text{Effort}}=\frac{400}{480}=0.833$

Since, efficiency $\left(\%\eta \right)=(\frac{\text{M.A.}}{\text{V.R.}}\times 100)\%$
$=(\frac{0.833}{1}\times 100)\%=83.3\%$