Question

A lever of length 14 cm has its load arm 5 cm long and effort arm is 9 cm long. (a) To which class does it belong? (b) Draw diagram of the lever showing the position of fulcrum F and directions of both the load L and effort E. (c) What is the mechanical advantage and velocity ration if the efficiency is 100% ? (d) What will be the mechanical advantage and velocity ration if the efficiency becomes 50%?

Answer 1

(a) It is second class lever

(b) Diagram is above

Load and effort are in opposite direction

$M.A=\frac{Loadlifted}{effortrequired}=\frac{L}{E}=\frac{9}{5}=1.8$

$V.R=\frac{distancemovedbyeffort}{distancemovedbyload}=\frac{M.A}{\eta }$

(c) If efficiency is $\eta =100$%$=1$

$\eta =\frac{M.A}{V.R}$

$V.R=\frac{1.8}{1}=1.8$

(d) If efficiency is $\eta =50$%$=0.5$

$\eta =\frac{M.A}{V.R}$

$V.R=\frac{1.8}{0.5}=3.6$