# quiz1 - Muraj Hamza – Quiz 1 – Due 10:00 pm – Inst...

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Unformatted text preview: Muraj, Hamza – Quiz 1 – Due: Feb 15 2006, 10:00 pm – Inst: Florin 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 2) 10 points Three objects can only move along a straight, level path. The graphs below show the po- sition d of each of the objects plotted as a function of time t . d t I d t II d t III The magnitude of the velocity k ~v k of the object increases in which of the cases? 1. I only 2. I, II, and III 3. II only 4. I and III only 5. II and III only 6. III only correct 7. I and II only Explanation: Case I: The object moves at constant speed. Case II: The object remains at rest. Case III: The speed of the object increases with time; i.e. , constant acceleration. Thus, the magnitude of the velocity of the object increases only in case III. 002 (part 2 of 2) 10 points The sum of the forces X F i = 0 on the object is zero in which of the cases? 1. I, II, and III 2. III only 3. I and II only correct 4. I only 5. II and III only 6. I and III only 7. II only Explanation: When the sum of the forces on the object is zero, the acceleration of the object is zero by Newton’s 2 nd law. In cases I and II, the velocity of the object doesn’t change with time, so the sum of the forces on the object is zero. In case III, the object is accelerating, so the sum of the forces on the object is not zero. 003 (part 1 of 2) 10 points Consider the 601 N weight held by two cables shown below. The left-hand cable had tension T 2 and makes an angle of θ 2 with the ceiling. The right-hand cable had tension 390 N and makes an angle of 42 ◦ with the ceiling. The right-hand cable makes an angle of 42 ◦ with the ceiling and has a tension of 390 N . 601 N T 2 3 9 N 4 2 ◦ θ 2 a) What is the tension T 2 in the left-hand cable slanted at an angle of θ 2 with respect to the wall? Correct answer: 446 . 795 N. Explanation: Observe the free-body diagram below. Muraj, Hamza – Quiz 1 – Due: Feb 15 2006, 10:00 pm – Inst: Florin 2 F 2 F 1 θ 1 θ 2 W g Note: The sum of the x- and y-components of F 1 , F 2 , and W g are equal to zero. Given : W g = 601 N , F 1 = 390 N , θ 1 = 42 ◦ , and θ 2 = 90 ◦- θ . Basic Concept: Vertically and Horizontally, we have F x net = F x 1- F x 2 = 0 = F 1 cos θ 1- F 2 cos θ 2 = 0 (1) F y net = F y 1 + F y 2-W g = 0 = F 1 sin θ 1 + F 2 sin θ 2-W g = 0 (2) Solution: Using Eqs. 1 and 2, we have F x 2 = F 1 cos θ 1 (1) = (390 N)cos42 ◦ = 289 . 826 N , and F y 2 = F 3- F 1 sin θ 1 (2) = 601 N- (390 N)sin42 ◦ = 601 N- 260 . 961 N = 340 . 039 N , so F 2 = q ( F x 2 ) 2 + ( F y 2 ) 2 = q (289 . 826 N) 2 + (340 . 039 N) 2 = 446 . 795 N ....
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quiz1 - Muraj Hamza – Quiz 1 – Due 10:00 pm – Inst...

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