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Unformatted text preview: Physics 204A THIRD EXAM Chapters 1 - 11 Spring 2007 1 Name:_________________________________________ Solve the following problems in the space provided. Use the back of the page if needed. Each problem is worth 20 points. You must show your work in a logical fashion starting with the correctly applied physical principles. The equations you need are on the equation sheet. Your score will be maximized if your work is easy to follow because partial credit will be awarded. 1. The four situations to the right show before and after "snapshots" of a car's velocity. Rank these situations, in terms of the impulse on the car required to create these changes in velocity, from most positive to most negative, All cars have the same mass. Explain your reasoning for full credit. The main principle is the Impulse-Momentum Theorem, r J = " r p . Using the definition of linear momentum, r p " m r v # r J = m r v $ m r v o . Calculating the change in momentum gives the impulse, A: J = m (20) " m (10) = 10 m B: J = m (0) " m (10) = " 10 m C: J = m ( " 10) " m (10) = " 20 m D: J = m (20) " m (20) = The ranking is, A>D>B>C. The ranking is, A>D>B>C....
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