Question

 You are using a wheel and axle as a simple machine. You applied a force of 30 lb to the rim 

of the wheel so that it can lift a load of 240 lb. The diameters of the wheel and axle are 3 feet 

and 4 inches, respectively. Determine the efficiency of the machine

Answer 1

$\eta F_1d_1=F_2d_2,$

$\eta =\frac{F_2}{F_1}\cdot \frac{d_2}{d_1},$

$\eta =\frac{240}{30}\cdot \frac{4}{12\cdot 3}=0.889=88.9\%.$