Question

A machine has a velocity ratio of 4. It is used to raise a load of 200 N by 4 m using an effort of 20 kgf. Find the work done on the machine. Take $g=10m{s}^{-2}$​.

• A. 1600 J
• B. 3200 J
• C. 6400 J
• D. 2000 J

Answer 1

The correct option is B

3200 J

Given, velocity ratio, V.R $=4$
Load $=200N$
Displacement $=4m$
Effort $=200kgf=20\times 10=200N$
Work done by machine = Load $\times$ Displacement= 200 $\times 4=800J$
Mechanical advantage, M.A = $\frac{load}{effort}$
= $\frac{200}{200}$ = 1.
Efficiency = $\frac{M.A}{V.R}$ = $\frac{1}{4}$.
Percentage efficiency = $\frac{1}{4}$ $\times$ 100 = 25%.
Work done on the machine (input) = $\frac{output}{efficiency}$ = $\frac{800}{\left(\frac{1}{4}\right)}=3200J$