Spring 11 Phys 121 - HW 01

# Spring 11 Phys 121 - HW 01 - dzifanu(sd26397 – HW 1 –...

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Unformatted text preview: dzifanu (sd26397) – HW 1 – opyrchal – (121102) 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A plastic rod is rubbed against a wool shirt, thereby acquiring a charge of − 4 . 9 μ C. The charge on an electron is 1 . 6 × 10 − 19 C. How many electrons are transferred from the wool shirt to the plastic rod? Correct answer: 3 . 0625 × 10 13 . Explanation: Let : q = − 4 . 9 μ C = − 4 . 9 × 10 − 6 C and e = − 1 . 6 × 10 − 19 C . The total charge is q = n e e n e = q e = − 4 . 9 × 10 − 6 C − 1 . 6 × 10 − 19 C = 3 . 0625 × 10 13 . 002 10.0 points A particle of mass 40 g and charge 63 μ C is released from rest when it is 67 cm from a second particle of charge − 12 μ C. Determine the magnitude of the initial ac- celeration of the 40 g particle. Correct answer: 378 . 4 m / s 2 . Explanation: Let : m = 40 g , q = 63 μ C = 6 . 3 × 10 − 5 C , d = 67 cm = 0 . 67 m , Q = − 12 μ C = − 1 . 2 × 10 − 5 C , and k e = 8 . 9875 × 10 9 . The force exerted on the particle is F = k e | q 1 || q 2 | r 2 = m a bardbl vectora bardbl = k e bardbl vectorq bardblbardbl vector Q bardbl m d 2 = k e vextendsingle vextendsingle 6 . 3 × 10 − 5 C vextendsingle vextendsingle vextendsingle vextendsingle − 1 . 2 × 10 − 5 C vextendsingle vextendsingle (0 . 04 kg) (0 . 67 m 2 ) = 378 . 4 m / s 2 . 003 10.0 points A particle with charge − 5 μ C is located on the x-axis at the point 6 cm , and a second particle with charge 4 μ C is placed on the x-axis at 8 cm . The Coulomb constant is 8 . 9875 × 10 9 N · m 2 / C 2 . 2 4 6 8 10 − 2 − 4 − 6 − 8 − 10 − 5 μ C 4 μ C − 8 μ C x → (cm) What is the magnitude of the total elec- trostatic force on a third particle with charge − 8 μ C placed on the x-axis at 2 cm ? Correct answer: 144 . 799 N. Explanation: Let : q 1 = − 5 μ C = − 5 × 10 − 6 C , q 2 = 4 μ C = 4 × 10 − 6 C , q 3 = − 8 μ C = − 8 × 10 − 6 C , x 1 = 6 cm = 0 . 06 m , x 2 = 8 cm = 0 . 08 m , and x 3 = 2 cm = 0 . 02 m ....
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Spring 11 Phys 121 - HW 01 - dzifanu(sd26397 – HW 1 –...

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