HW 4-2-solutions

# HW 4-2-solutions - madrid(tmm2353 HW 4-2 Antoniewicz(56445...

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madrid (tmm2353) – HW 4-2 – Antoniewicz – (56445) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 8.0 points IF a chain oF 30 identical short springs linked end to end has a sti±ness oF 220 N / m, what is the sti±ness oF one short spring? Correct answer: 6600 N / m. Explanation: Springs in series have the e±ective sti±ness K , where K is given in terms oF the sti±nesses oF the individual springs as Follows: 1 /K = 1 /k 1 + 1 /k 2 + · · · + 1 /k N . ²or identical springs, we have k = NK , where k is the sti±ness oF a single spring. ThereFore k = (30)(220 N / m) = 6600 N / m . 002 8.0 points You place 35 identical springs side by side (in parallel) and connect them to a large, massive block. The sti±ness oF the 35-spring combi- nation is 20025 N / m. What is the sti±ness oF one oF the individual springs? Correct answer: 572 . 143 N / m. Explanation: Springs in parallel have an e±ective sti±ness K , where K is given in terms oF the sti±nesses oF the individual springs as Follows: K = k 1 + k 2 + · · · + k N . ²or identical springs, we have K = Nk , or k = K/N , where k is the sti±ness oF a single spring. ThereFore, k = 20025 N / m 35 = 572 . 143 N / m . 003 (part 1 of 4) 3.0 points One mole oF tungsten (6 . 02 × 10 23 atoms) has a mass oF 184 g, and its density is 19 . 3 g / cm 3 , so the center-to-center distance between atoms is 2 . 51 × 10 - 10 m. You have a long, thin bar oF tungsten, 2 . 2 m long, with a square cross section, 0 . 13 cm on a side. You hang the rod vertically and attach a 420 kg mass to the bottom, and you observe that the bar becomes 1 . 32 cm longer. ²rom these measurements, it is possible to determine the sti±ness oF one interatomic bond in tungsten.

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HW 4-2-solutions - madrid(tmm2353 HW 4-2 Antoniewicz(56445...

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