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Unformatted text preview: Version One – Homework 6 – Heinz – 81204 – Sep 30, 2004 1 This printout should have 18 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Serway CP 05 60 07:03, trigonometry, numeric, > 1 min, nor mal. 001 (part 1 of 1) 10 points A block of mass 12 kg slides from rest down a frictionless 35 ◦ incline and is stopped by a strong spring with a spring constant 30000 N / m. The block slides 3 m from the point of release to the point where it comes to rest against the spring. The acceleration of gravity is 9 . 8 m / s 2 . When the block comes to rest, how far has the spring been compressed? Correct answer: 0 . 116149 m. Explanation: Let PE = 0 at the point where the block comes to rest against the spring. Given : m = 12 kg θ = 35 ◦ , k = 30000 N / m , and ‘ = 3 m . Conservation of Mechanical Energy gives us U g,i = U s,f mg L sin θ = 1 2 k d 2 d 2 = 2 mg ‘ sin θ k d = r 2 mg ‘ sin θ k = s 2(12 kg)(3 m)(9 . 8 m / s 2 ) 30000 N / m · √ sin35 ◦ = . 116149 m . Spring Constant 03 07:03, trigonometry, numeric, > 1 min, nor mal. 002 (part 1 of 2) 5 points An archer pulls her bow string back 0 . 4 m by exerting a force that increases uniformly from zero to 230 n. What is the equivalent spring constant of the bow? Correct answer: 575 n / m. Explanation: F = k x, so k = F x = 230 n . 4 m = 575 n / m . 003 (part 2 of 2) 5 points How much work is done in pulling the bow? Correct answer: 46 J. Explanation: The work done is transferred to potential energy of the bow W potential = U = 1 2 k x 2 = 1 2 (575 n / m)(0 . 4 m) 2 = 46 J . AP B 1998 MC 59 60num 07:04, trigonometry, numeric, > 1 min, nor mal. 004 (part 1 of 2) 5 points A rock of mass 0 . 8 kg is thrown horizontally off a building from a height 1 . 2 m. The speed of the rock as it leaves the thrower’s hand at the edge of The building is 1 . 6 m / s, as shown. The acceleration of gravity is 9 . 81 m / s 2 . 1 . 6 m / s 1 . 2m Δ x Version One – Homework 6 – Heinz – 81204 – Sep 30, 2004 2 How much time does it take the rock to travel from the edge of the building to the ground? Correct answer: 0 . 494619 . Explanation: The motion of the rock in the ydirection is a free falling motion from rest, d = 1 2 g t 2 . Thus, h = 1 2 g t 2 , so t = s 2 h g = s 2(1 . 2 m) (9 . 81 m / s 2 ) = 0 . 494619 s . 005 (part 2 of 2) 5 points What is the kinetic energy of the rock just before it hits the ground? Correct answer: 10 . 4416 . Explanation: We can use workenergy theorem, K f K i = W , where in the present problem, W = ( mg ) h , and K i = 1 2 mv 2 ....
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This note was uploaded on 07/02/2011 for the course PHYS 201 taught by Professor Woodahl during the Fall '09 term at Indiana.
 Fall '09
 WOODAHL
 Physics, Work

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