# PHYSICS1 - Physics Exam 1(80 Minutes Maximum points 120...

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Physics : Exam 1 (80 Minutes, Maximum points: 120) Multiple choice questions 1-6: 10 points each 1. To the right is a free body diagram for a shoe sitting at rest on a tilted floor tile (tilted at an angle θ above the horizontal.) Identify all the mistakes in the free-body diagram. (a) r N S on Sh should be pointing vertically upwards (b) r N S on Sh is drawn too long (c) There is no friction in this situation (d) Both (a) and (b) are mistakes in the free-body diagram (e) Both (b) and (c) are mistakes in the free-body diagram 2. You are traveling in a car and when you are 40 m from a traffic light, you see it turn yellow. You are traveling at 20 m/s. You immediately hit the brakes (ignore any reaction time). You slow down at a rate of 8 m/s every second. Which of the following equations best represents the subsequent position of the car as a function of time? (Treat the moment you hit the brakes as the starting clock reading t = 0, take the traffic light as the origin of the co-ordinate system.) (a) x ( t ) = 40m + (20m /s) t + 1 2 ( - 8m /s 2 ) t 2 (b) x ( t ) = 40m + (20m /s) t + 1 2 (8m /s 2 ) t 2 (c) x ( t ) = 40m + ( - 20m /s) t + 1 2 ( - 8m /s 2 ) t 2 (d) x ( t ) = 40m + ( - 20m /s) t + 1 2 (8m /s 2 ) t 2 (e) Both (a) and (d) are correct. 3. You pull a 30-kg suitcase along the ground by means of a strap, which exerts a force of magnitude 50 N at an angle of 40 ° above the horizontal. What answer is closest to the magnitude of the normal force exerted by the ground on the suitcase? You can assume that the ground is smooth. (a) 32N (b) 38N (c) 50N (d) 268N (e) 300N 4. Imagine a book sitting on a table. Identify the third law pair force(s) of the forces shown in the free-body diagram for the book, shown to the right. (a) Newton’s third law applies to two interacting objects and there is only one object shown in the free-body diagram.

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