CU 2009 sp exam3 key

CU 2009 sp exam3 key - 1 of 10 vers 0001 4/7/2009 Exam III,...

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Unformatted text preview: 1 of 10 vers 0001 4/7/2009 Exam III, vers. 0001 - Physics 2010 - Sping, 2009 NAME_______________________________________________________ Signature_____________________________________________________ Student ID #__________________________________________________ Circle your TAs Name : Uriel Nauenberg, Alysia Marino, Gabriel Ycas, Weisen Shen, Chen Zhang, Joseph Yelk, Qi Hu Please write the DAY/START TIME of your recitation/lab section in the box. Enter Mon/10am, Tues/Noon, etc. Please do not open the exam until you are told to. Your exam should have 11 pages, numbered 1 thru 11. The last sheet is for scratch paper. This exam consists of 25 questions, worth 4 points each for a total of 100 points. Fill in the bubble sheet with a #2 pencil. Please fill out your bubble sheet according to the following instructions or you will automatically lose 10 points . Check each box as you complete the instructions. Please circle your TA's name above and place DAY/START TIME in box. Print and bubble in your name on the bubble sheet. Print and bubble in your student Identification Number. Print and bubble in your Exam version, 0001 or 0002, in the upper left of your bubble sheet in the area marked 1234. Erase mistakes as thoroughly as possible. Ask for a fresh bubble sheet if you fear you cannot thoroughly erase mistakes. As you take the exam, circle the correct answers on your exam and mark them on the bubble sheet. That way we can grade the exam, if your bubble sheet is lost. Possibly useful information: The magnitude of the acceleration of gravity: g = 9.8 m/s 2 . ~ 3.14. G = 6.67 x 10-11 Nm 2 /kg 2 . I ring = MR 2 I disk = (1/2) MR 2 I sphere = (2/5) MR 2 I Hollow Sphere = (2/3) MR 2 2 of 10 vers 0001 4/7/2009 1. A box of mass m = 10 kg is lifted up (against gravity) at a constant velocity for a distance of 5 m. How much work was done in lifting the box? A) 490 J B) -50 J C) 50 J D) -980 J E) -490 J W = Fx = mgx = (10)(9.8)(5) J = 490 J 2. A 1000 kg car brakes to a stop from an initial speed of 30 m/s. How much work was done on the car to get it to stop? A) 9.0 x 10 5 J B) 3.0 x 10 4 J C) 3.0 x 10 4 kg m/s D) 4.5 x 10 5 J E) 4.5 x 10 4 J W= | KE| = mv 2 = 9.5(10 3 )(30) 2 J = 4.5 x 10 5 J 3. A book is dragged along rough table at constant velocity with a force F ext = 10 N for a distance of 1 m. What is the work done on the book by friction? A) -10 J B) 10 J C) -5 J D) 5 J E) Impossible to tell from the information given. v constant means that F f = -F ext = -10 N. So, W f = F f x = (-10)(1) J = -10 J 4. A rock of mass 1 kg is swung in a horizontal circle of radius 1 m by a force F = 100 N. Whats the work done on the rock by the force F? A) 0 B) 5 J C) 9.8 J D) 10 J E) 19.6 J F is perpendicular to the displacement of the rock, so no work is done by it. 3 of 10 vers 0001 4/7/2009 5. The work W accelerates a car from 0 to 25 km/h. How much work is needed to accelerate the car from 25 km/h to 50 km/h?...
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CU 2009 sp exam3 key - 1 of 10 vers 0001 4/7/2009 Exam III,...

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