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Unformatted text preview: pasha (sep635) HW 63 Antoniewicz (56445) 1 This printout should have 14 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 4.0 points A mass of 0 . 22 kg hangs from a vertical spring in the lab room. You grab hold of the mass and throw it vertically downward. The speed of the mass just after leaving your hand is 3 . 38 m / s . While the mass moved downward a distance of 0 . 07 m, how much work was done on the mass by the Earth? Use g = 9 . 8 m / s 2 . Correct answer: 0 . 15092 J. Explanation: We can write W Earth = ~ F ~ r = h , mg, i h , y, i = (0 . 22 kg)(9 . 8 m / s 2 )(3 . 38 m / s) = . 15092 J . 002 (part 2 of 2) 4.0 points The speed of the mass has decreased to 2 . 83 m / s. How much work was done on the mass by the spring? Correct answer: . 526625 J. Explanation: We can write KE = W spring + W Earth W spring = KE W Earth = 1 2 m ~ v f 2 1 2 m  ~ v i  2 W Earth = . 526625 J . 003 (part 1 of 6) 2.0 points A lithium nucleus has mass 5 . 1 10 27 kg. If its speed is 0 . 986 c (that is, v/c = 0 . 986), what is the particle energy? Use c = 3 10 8 m / s. Correct answer: 2 . 7527 10 9 J. Explanation: The particle energy is just the total energy, given by E = mc 2 . So we have E = 1 s 1 v c 2 mc 2 = 1 p 1 . 986 2 (5 . 1 10 27 kg) c 2 = 2 . 7527 10 9 J . 004 (part 2 of 6) 2.0 points What is the rest energy? Correct answer: 4 . 59 10 10 J. Explanation: The rest energy is just E rest = mc 2 = (5 . 1 10 27 kg) c 2 = 4 . 59 10 10 J . 005 (part 3 of 6) 2.0 points What is the kinetic energy? Correct answer: 2 . 2937 10 9 J. Explanation: The kinetic energy is given by KE = E E rest = 2 . 7527 10 9 J 4 . 59 10 10 J = 2 . 2937 10 9 J ....
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 Fall '08
 Turner
 Mass

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