4. What is the net force acting on the following object: Justify your choice with mathematics. 452 N [up] 54N [W] 72 N [E] * 52 N [down] a. 70 N [E] b. 70 N [W] C. 18 N [W] d. 18 N [E] 5. Which of the following situations does this free-body diagram represent? Explain your choice. FN F. a. A mug sits on a desk. b. An object is in free fall. c. Two students are playing tug-of-war. d. A student kicks a soccer ball off of the ground