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p14mt2_w09

# p14mt2_w09 - Physics 14 Midterm#2 Winter 2009 SHOW ALL YOUR...

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Physics 14 - Midterm #2 - Winter 2009 SHOW ALL YOUR WORK AND REASONING 1. (12 pts) Two train engines of the same mass collide with each other. Immediately after the collision, the trains are seen to be moving slowly to the left , stuck together. a) Draw a diagram below carefully showing them and their velocity vectors just before and then just after they collide. b) Which train’s momentum changed most during the collision, and why? c) Train 1 had a speed of 20 m/s just before the collision, and their speed when stuck together after the collision is 6 m/s to the left. What was the speed of Train 2 just before the collision? e) Do you think the total kinetic energy of the trains before and after the collision is the same? Why or why not? Before After

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Physics 14 - Midterm #2 - Winter 2009 2. (4 pts) A mass (4 kg) is initially seen to be moving horizontally at 6 m/s on a frictionless surface. You push on it, against the way it is moving, and slow it down to a speed of 4 m/s. How much work did you do on it? If you pushed on it with a force of 10.0 N, how far did it travel during that time? 3. (4 pts) If a sound becomes louder, which wave characteristic(s) is/are likely to be de creasing – frequency, wavelength, amplitude, or speed? If a sound’s pitch in creases, which wave characteristic(s) is/are likely to be de creasing – frequency, wavelength, amplitude, or speed?
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