A student wants to determine the coefficients of static friction and kinetic friction between a box and a plank. She places the box on the plank and gradually raises one end of the plank. When the angle of inclination with the horizontal reaches 30°, the box starts to slip, and it slides 2.5 m down the plank in 3.7 s at constant acceleration.
(a) What is the coefficient of static friction?
(b) What is the coefficient of kinetic friction?