A student wants to determine the coefficients of static frictionand kinetic friction between a box and a plank. She places the boxon the plank and gradually raises one end of the plank. When theangle of inclination with the horizontal reaches 40°, the box starts to slip, and it slides2.8 m down the plank in 3.6 s.
(a) What is the coefficient of static friction?
(b) What is the coefficient of kinetic friction?