Step by step text solution for A child pushes a box that has mass m up an incline plane at an angle alpha above the horizontal. The coefficients of friction between the incline and the box are mu_(s) and mu_(k). The force applied by the child is horizontal, (a )If mu_(s) is greater than some critical value, the child cannot start the box moving up the incline, no matter how hard he pushes. Calculate this critical value of mu_(s). (b) Assume that mu_(s) is less than this critical value. What magnitude of force must the child apply to keep the box moving up the plane at constant speed. [cot alpha,(mg(sinalpha+mu_(k)cosalpha))/(cosalpha-mu_(k)sinalpha)] by PHYSICS experts to help you in doubts & scoring excellent marks in Class 11 exams.