4. A block of wood on a horizontal surface may have two horizontal forces, F, and F2, acting on it. Either force may pull to the left or right. (The normal force and force due to gravity are equal and opposite and may be ignored for this exercise.) Complete the chart below by providing the missing force values, direction (left or right), and use vector arrows to draw the two forces, F, and F2 on the diagram. Description of Net F1 (N) F2 (N) Diagram motion force (N) a. Stationary 10 left b. Moving to the right at a 5 left constant velocity C. Accelerating to the left 25 left 10 left . d. Accelerating to the left 25 20 right 5. A certain sled has a weight of 52 N. A horizontal force of 18 N is required to pull the sled across a level cement sidewalk at constant velocity. Determine the coefficient of friction between the sidewalk and the metal runners of the sled. [0.351 6. A sled having a weight of 702 N is placed on packed snow. Determine the magnitude of the force necessary to slide the sled across the level snow at a constant velocity. The coefficient of friction is 0.012 for the sled runners on packed snow. [8.4 N]