Question

In a lifting machine, the efforts required for lifting loads of $20$ N and $30$ N were $5$ N and $6$ N respectively. If the velocity ratio of the machine is $20$, determine efficiencies corresponding to loads of $20$ N and $30$ N

• A. 25 % and 20%
• B. 35% and 55%
• C. 30% and 50%
• D. 60% and 65%

Answer 1

Answer: (A)

25 % and 20%

Let us take first case,

in which $load=20N,effort=5N,VR=20$

$Efficiency=\frac{load}{VR\ast effort}\ast 100$

Putting above values, we get

$Efficiency=\frac{20}{20\ast 5}\ast 100=20$

In second case we have. $load=30N,efoort=6N,VR=20$

$Efficiency=\frac{load}{VR\ast effort}\ast 100$

Putting values we get,

$Efficiency=\frac{30}{20\ast 6}\ast 100=25$

Hence$Efficiency=25$