The radius of the axle is 3", the radius of the wheel is 6" and the blue box weighs 35 lbs. What is the effort force necessary to balance the load?

The mechanical advantage (MA) of a wheel and axle is the input radius divided by the output radius. In this case, the input radius (where the effort force is being applied) is 6 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of 6 / 3 = 2.

\(M A=\frac{\text { load }}{\text { effort }} \text { so, effort }=\frac{\text { load }}{M A}=\frac{35 l b s .}{2}=17.50 \mathrm{lbs}\)