Serway & Jewett — Static Equilibrium and Elasticity: Problem 19

A child slides across a floor in a pair of rubber-soled shoes. The friction force acting on each foot is \(20.0 \text{ N}\). The footprint area of each shoe sole is \(14.0 \text{ cm}^2\), and the thickness of each sole is \(5.00 \text{ mm}\). Find the horizontal distance by which the upper and lower surfaces of each sole are offset. The shear modulus of the rubber is \(3.00 \text{ MN/m}^2\).