A tired and overloaded student is attempting to hold a large physics textbook wedged under his arm. The textbook has a mass of 3.0 kg, while the coefficient of static friction of the textbook against the student's underarm is 0.320 and the coefficient of static friction of the book against the student's shirt is 0.160.
(a) What is the minimum horizontal force that the student must apply to the textbook to prevent it from falling?
(b) If the student can only exert a force of 65.3 N, what is the acceleration of the textbook as it slides from under his arm? The coefficient of kinetic friction of arm against textbook is 0.200, while that of shirt against textbook is 0.090.
What is the magnitude?
What is the direction?