Question 1: Alex is asked to move two boxes of books in contact with each other and resting on a rough floor. He decides to move them at the same time by pushing on box A with a horizontal pushing forceFP=9.5N.Here A has a massmA=11.0kgand B has a massmB= 7.0 kg.The contact force between the two boxes isFC.The coefficient of kinetic friction between the boxes and the floor is0.04. (AssumeFPacts in the +xdirection.)
1. What is the magnitude of the acceleration of the two boxes? ________m/s2
2. What is the force exerted on mB by mA? In other words what is the magnitude of the contact force FC? _______N
3. If Alex were to push from the other side on the 7.0-kg box, what would the new magnitude of FC be? ________N
Questions 2 : A book of mass 9 kg rests on a plank. You tilt one end of the plank and slowly increase the angle of the tilt. The coefficient of static friction between the book and the plank is 0.22. What is the maximum angle of tilt for which the book will remain stationary and not slide down the plank?
_________degrees