On a factory assembly line, boxes of mass 20 kg slide from rest down a frictionless incline of length 10m angled 20 degrees below the horizontal. The boxes slide horizontally across a ramp of unknown kinetic coefficient of friction, coming to rest over a distance of 15m where a worker picks them up.
What is the speed of the boxes at the bottom of the incline?
What is the coefficient of friction between the box and horizontal ramp?