Question

A boy lifts a load of 400 N through a vertical height of 5 m by a fixed pulley by applying an effort of 480 N at the other end.
Find the efficiency.

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

Answer 1

The correct option is A

83.3%

Given, load = 400 N
Effort = 480 N
Distance moved by effort end = distance moved by load end = 5 m

Velocity Ratio (VR) $=\frac{Distancemovedbyeffort}{Distancemovedbyload}=\frac{5}{5}=1$

Mechanical advantage (MA) $=\frac{Load}{Effort}=\frac{400}{480}=0.833$
Since, efficiency % $\left(\eta \right)=(\frac{MR}{VR}\times 100)\%$
$=(\frac{0.833}{1}\times 100)\%$ = 83.3%