# hw9(1) - lenoir (wml297) oldhomework 09 Turner (58220) This...

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lenoir (wml297) – oldhomework 09 – Turner – (58220) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A 5 . 2 kg block initially at rest is pulled to the right along a horizontal, Frictionless surFace by a constant, horizontal Force oF 16 . 5 N. ±ind the speed oF the block aFter it has moved 4 . 9 m. Correct answer: 5 . 57639 m / s. Explanation: Let : m = 5 . 2 kg , F = 16 . 5 N , and Δ x = 4 . 9 m . The acceleration oF the block is a = F m = 16 . 5 N 5 . 2 kg = 3 . 17308 m / s 2 . Since the Force is constant, the acceleration is constant. We fnd the fnal speed oF the block using the equation v f = r v 2 0 + 2 a ( x f - x 0 ) = r 2 (3 . 17308 m / s 2 ) (4 . 9 m) = 5 . 57639 m / s . 002 (part 1 oF 2) 10.0 points A string is tied to a book and pulled at an angle α as shown in the diagram. The book remains in contact with the table and does not move. m μ s T α Which choice best describes the Free body diagram in the vertical direction For this situ- ation? 1. N = m g 2. N = m g + T cos α 3. N = m g + T sin α 4. N = m g - T cos α 5. N = m g - T sin α correct Explanation: m string α m g N μ s N Because the string is pulling partially up, the Force oF the table on the book (the normal Force) is less than iF the string were not there. s F y : N + T sin α = m g N = m g - T sin α . 003 (part 2 oF 2) 10.0 points Which Forces must change in order For the book to start moving? 1. normal 2. None oF these 3. normal, Friction, and tension in the string correct 4. gravitational 5. Friction 6. tension in the string 7. normal and gravitational 8. Friction and tension in the string

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lenoir (wml297) – oldhomework 09 – Turner – (58220) 2 9. friction, tension in the string, and gravi-
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## This note was uploaded on 04/15/2010 for the course PHY 12343 taught by Professor Turner during the Spring '10 term at University of Texas at Austin.

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hw9(1) - lenoir (wml297) oldhomework 09 Turner (58220) This...

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