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Unformatted text preview: homework 13 – YOO, HEE – Due: Feb 19 2008, 4:00 am 1 Question 1, chap 6, sect 2. part 1 of 1 10 points A load of 30 N attached to a spring hanging vertically stretches the spring 6 . 4 cm. The spring is now placed horizontally on a table and stretched 12 cm. What force is required to stretch it by this amount? Correct answer: 56 . 25 N (tolerance ± 1 %). Explanation: Given : F = 30 N , x 1 = 6 . 4 cm , and x 2 = 12 cm . The force exerted by the spring is F 1 = k x 1 k = F 1 x 1 . When stretched 12 cm, F 2 = k x 2 = F 1 x 2 x 1 = (30 N) (12 cm) 6 . 4 cm = 56 . 25 N . Question 2, chap 6, sect 2. part 1 of 2 10 points A 0 . 207 kg mass is attached to a spring with a spring constant 163 N / m so that the mass is allowed to move on a horizontal frictionless surface. The mass is released from rest when the spring is compressed 0 . 134 m. Find the maximum force on the mass. Correct answer: 21 . 842 N (tolerance ± 1 %). Explanation: Basic Concepts: F = ma F = k x The maximum force and acceleration occur at the maximum amplitude of the motion. Solution: The force on the mass is F = k x = (163 N / m) (0 . 134 m) = 21 . 842 N . Question 3, chap 6, sect 2. part 2 of 2 10 points Find the maximum acceleration. Correct answer: 105 . 517 m / s 2 (tolerance ± 1 %). Explanation: The acceleration is a = F m = 21 . 842 N . 207 kg = 105 . 517 m / s 2 . Question 4, chap 6, sect 3. part 1 of 2 10 points The coefficient of static friction between the person and the wall is 0 . 73 . The radius of the cylinder is 6 . 6 m . The acceleration of gravity is 9 . 8 m / s 2 . An amusement park ride consists of a large vertical cylinder that spins about its axis fast enough that any person inside is held up against the wall when the floor drops away. ω 6 . 6 m What is the minimum angular velocity ω min needed to keep the person from slip ping downward? Correct answer: 1 . 4262 rad / s (tolerance ± 1 %). Explanation: homework 13 – YOO, HEE – Due: Feb 19 2008, 4:00 am 2 Let : R = 6 . 6 m and μ = 0 . 73 ....
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This note was uploaded on 05/04/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.
 Spring '08
 Turner
 Force, Mass, Work

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