INTRODUCTION: This is a problem from my Introduction to Physical Science class using "Conceptual Physics" 10th Ed.by Paul G. Hewitt EXACT PROBLEM: "A 15-N cart rests in the isle of a jet airplane that is cruising horizontally at a constant velocity. The coefficient of static friction between the cart and the floor is 0.4, while the coefficient of kinetic friction is 0.2." PROBLEMS FACED: Determine the frictional force acting on the cart. MY THOUGHTS: I don't know what to do here really. I am not sure which formulas to use.