A box with mass m is dragged across a level floor having a coefficient of kinetic friction μk by a rope that is pulled upward at an angle (J above the horizontal with a force of magnitude F.
(a) In terms of m, μk, (J, and g, obtain an expression for the magnitude of force required to move the box with constant speed.
(b) Knowing that you are studying physics, a CPR instructor asks you how much force it would take to slide a 90-kg patient across a floor at constant speed by pulling on him at an angle of 250 above the horizontal. By dragging some weights wrapped in an old pair of pants down the hall with a spring balance, you find that μk = 0.35. Use the result of part (a) to answer the instructor's question.