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PLC Activity #7 Practice Exam 1.1 All problems are worth 20 points Problem 1 A car traveling 15.6 m/s is 24.0 m from a barrier when the driver slams on the brakes. The car hits the barrier 2.00 s later. a. What is the car’s constant deceleration before impact? Answer: −3.56 m/s2 b. How fast is the car traveling at impact? Answer: 8.43 m/s Problem 2 Bond, James Bond, is escaping across a rooftop and runs off the roof horizontally at a speed of 5.3 m/s, hoping to land on the roof of an adjacent building. The horizontal distance between the two buildings is 12 feet, and the roof of the adjacent building is 2.0 m below the jumping-off point. Does James Bond make the jump? That is, is James Bond able to land on the adjacent building? If not, by how much did he miss? (Hint: 1 ft = 0.304 m) Answer: No, 10 inches Problem 3 A student, crazed by the first physics Midterm, uses a pushing force of 80 N angled at 70° to push a 5.0 kg book across the frictionless ceiling of his room. a. What is the block's acceleration? Answer: 5.5 m/s2 b. What is the force of the ceiling on the book? Answer: 26 N Problem 4 A block of mass 5.00 kg is pulled along a horizontal frictionless floor by a cord that exerts a force of 12.0 N at an angle of 250 above the horizontal. a. What is the block's acceleration? (b) What is the force of the floor? Answer: 2.18 m/s2 b. What is the force of the floor? Answer: 43.9 N Problem 5 Use short concise sentences to answer the following questions using physics principles. Make sure to explain your reasoning for each answer a. Can an object be increasing in speed as its acceleration decreases? If so, give an example and draw the motion diagram. b. A cart rolling at constant velocity fires a ball straight up. When the ball comes down will it land in front of the lunching tube, behind the launching tube, or directly in it? c. Why does a child in a wagon seem to fall backward when you give the wagon a sharp pull? d. A woman in an elevator lets go of her briefcase but it does not fall to the floor. Use Newton’s 2nd law to explain how the elevator is moving?