The diagram above is a block and tackle pulley system in which an effort of 80N is use to lift a load of 240N. The efficiency of the machine is
Attached Figure / Diagram
A
60%
B
50%
C
40%
D
33%
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Since the number of pulleys present is 6, it implies that the velocity ratio V.R = 6
Efficiency = \(\frac{\text{M.A}}{\text{V.R}}\times \frac{100}{1}\)
= \(\frac{Load}{Effort}\times\frac{1}{V.R}\times\frac{100}{1}\)
= \(\frac{240}{80} \times\frac{1}{6} \times\frac{100}{1}\)
= 50%
∴ Efficiency = 50%
Source: Myschool Past Questions Archive (Record #11818)