Exam2Solution-EP1-S08

Exam2Solution-EP1-S08 - Engineering Physics 1 (Phys. 213)...

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7 Engineering Physics 1 (Phys. 213) Exam 2 Solution, Feb. 22 nd , 2008 (O’Shea) Name __________________________________ Instructions: Please Read! This is a closed book, closed notes exam. This exam contains multiple-choice questions and problems. For each multiple-choice question, circle the letter of the best response. For problems, you need to show your work in a professional manner and write the final numerical answer with the proper unit in the space shown. Numerical answers without supporting calculations will receive zero credit. Partial credit is available only if your work is clear. 1. Academic honesty statement. This exam will NOT be marked unless you sign the academic honesty statement below. Your signature indicates that you have read , understood , and complied with the meaning of this statement. On my honor as a student I have neither given nor received unauthorized aid on this assignment. Sign your name:__________________________________________________________ 2. (1 point) Circle your Studio instructor/hour: Lynch /TU 9:30 Matloob /TU 11:30 Regehr /TU 1:30 O’Shea/WF 7:30 Lynch /WF 9:30 Page total: /1 Page total: /15 Total: /100
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8 3 . A worker pulls on a 12 kg crate with a force of magnitude F 1 = 110 N at θ = 30 0 below the horizontal as shown. The coefficient of static friction between the crate and the floor is 0.60. a) (6 points) What is the value of the maximum value of the static friction force? F N - F 1 sin mg = ma y = 0. f S,max = μ s F N = s ( mg + F 1 sin ) = (0.60) [(12 kg)(9.8 m/s 2 ) + (110 N)sin30 0 ] = 104 N b) (4 points) Does the crate move? [No credit for yes/no answer, must show working!] First check to see if the crate is stationary: find value of f required to keep crate stationary F 1 cos θ - f = 0 f = F 1 cos θ = 95.3 N Since f < f s , max it does not move. 4 . (8 pts) A 4.0 kg breadbox on a frictionless incline of angle θ = 50° is connected, by a string that runs over a pulley, to a light spring of spring constant k = 120 N/m, as shown. The box is released from rest when the spring is unstretched. Assume that the pulley is massless and frictionless. How far down the incline from its point of release does the box slide before momentarily stopping? Use work –kinetic energy
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Exam2Solution-EP1-S08 - Engineering Physics 1 (Phys. 213)...

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