Test #1- PHY 302L

# Test #1- PHY 302L - Version 006/AAABC Test#1...

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Version 006/AAABC – Test #1 – Antoniewicz – (56495) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Two spheres, fastened to “pucks”, are rid- ing on a frictionless airtrack. Sphere 1 is charged with 2 nC, and sphere 2 is charged with 8 nC. Both objects have the same mass. 1 nC is equal to 1 × 10 9 C. As they repel, 1. they do not accelerate at all, but rather separate at constant velocity. 2. sphere 1 accelerates 4 times as fast as sphere 2. 3. sphere 1 accelerates 16 times as fast as sphere 2. 4. sphere 2 accelerates 16 times as fast as sphere 1. 5. they have the same magnitude of acceler- ation. correct 6. sphere 2 accelerates 4 times as fast as sphere 1. Explanation: The force of repulsion exerted on each mass is determined by F = 1 4 π ǫ 0 Q 1 Q 2 r 2 = m a where r is the distance between the centers of the two spheres: bardbl vector F 12 bardbl = bardbl vector F 21 bardbl . Since both spheres have the same mass and are subject to the same force, they have the same acceleration. 002 10.0 points The two charges Q are fixed at the vertices of an equilateral triangle with sides of length a as shown. a a a Q Q q The work required to move a charge q from the other vertex to the center of the line join- ing the fixed charges is 1. W = 2 k Q q a correct 2. W = 6 k Q q a 3. W = 3 2 k Q q a 4. W = 0 5. W = 2 2 k Q q a 6. W = 2 k Q q a 7. W = 4 k Q q a 8. W = 3 k Q q a 9. W = k Q q a 10. W = 6 3 k Q q a Explanation: U 1 = + k Q q a + k Q q a = +2 k Q q a U 2 = + k Q q a 2 + k Q q a 2 = +4 k Q q a W = U 2 U 1 = 2 k Q q a . 003 10.0 points The total charge that an automobile battery can supply without being recharged is given

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Version 006/AAABC – Test #1 – Antoniewicz – (56495) 2 in terms of Ampere-hours. A typical 12-V battery has a rating of 65 A · h . Suppose you forget to turn off the headlights in your parked automobile. If each of the two headlights draws 1 . 8 A , find out the time before your battery is “dead”. 1. 9.5 2. 6.57143 3. 14.0385 4. 11.6667 5. 18.0556 6. 16.1765 7. 14.6875 8. 9.7561 9. 6.71053 10. 14.2 Correct answer: 18 . 0556 h.
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