hw 12 sol

# hw 12 sol - Patel (pnp223) homework 12 Turner (92160) This...

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Patel (pnp223) – homework 12 – Turner – (92160) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A passenger on a ±erris wheel moves in a vertical circle at constant speed. Are the Forces on her balanced? 1. Yes; the speed is constant. 2. No; there is an inward net Force. correct 3. No; the direction oF net Force does not change. 4. Yes; it moves in a vertical circle. Explanation: Even though she moves at constant speed, she does not move in a straight line, so, by Newton’s frst law, the Forces on her are not balanced. The net Force is inward since the ±erris wheel moves in a circle. 002 10.0 points A dancer moves around an elliptical path with a constant speed. S P R Q Which oF the Following best represents the magnitude oF the dancer’s acceleration as a Function oF time t during one trip around the path, beginning at point P ? 1. t a t P t Q t R t S t P 2. t a t P t Q t R t S t P 3. t a t P t Q t R t S t P 4. None oF these graphs is correct. 5. t a t P t Q t R t S t P 6. t a t P t Q t R t S t P 7. t a t P t Q t R t S t P 8. t a t P t Q t R t S t P correct 9. t a t P t Q t R t S t P Explanation: During RS and PQ , the acceleration is zero because the velocity is a constant both in mag- nitude and in direction. During QR and SP , even though the magnitude oF the velocity is a constant, it changes its direction, which re- sults in an acceleration oF v 2 r , where v is the velocity and r is the radius oF the arc. So the

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## This note was uploaded on 07/11/2009 for the course PHY 92160 taught by Professor Turner during the Spring '09 term at University of Texas.

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hw 12 sol - Patel (pnp223) homework 12 Turner (92160) This...

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