1. What force is required to drag a sack of rice weighing 105 lb if the coefficient of friction is 0.25?
(a) when the force is parallel to the surface,
(b) when the force makes 37° above the horizontal.
2. A piano weighing 600 lb is to be raised to a platform 4 ft high through a plank 10 ft long. If the coefficient of friction is 0.30, what force parallel to the plank will be needed?