Solution:
Given,
Load (L) = 600 N.
Load distance (LD) = 30 cm,
Length of the lever (l) = 90 cm,
∴ Effort distance (ED) = l - LD = 90 cm - 30 cm = 60 cm
At equlibrium,
Effort, \(E=\frac{L\times LD}{ED}=\frac{600\times30}{60}=300N\)
Then, mechanical advantage
\(MA=\frac LE=\frac{600}{300}=2\)
And, velocity ratio is given by
\(VR=\frac{ED}{LD}=\frac{60}{30}=2\)
Finally, the efficiency (η) of the lever is given by the formula as
efficiency, \(\eta=\frac{MA}{VR}\times100\%\)
Or, \(\eta=\frac22\times100\%\)
∴ η = 100 %
Hence, the efficiency of this lever is 100%. This is an ideal machine, because in real life due to friction and other conditions the efficiency of machine will always be less than 100%.