PHY 2048 Midterm: 2048_Fall16_Exam3_Solution
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The two forces are equal and opposite: momentum is conserved. So |vb| = (3/2)|va| (not surprising that b goes faster) 2/mbvb: we can use the simple kinematic equation that v = v0 + at and take up as positive. v = +2. 0 -9. 8*1 = -7. 8 m/s. so speed is 7. 8 m/s, average velocity is displacement/time. Displacement is distance in a straight line between beginning and ending points. If you sketch the function you find that it has a minimum between x=0 and x=-2. It is when u is a minimum then v is a maximum. To find this location, differentiate u and set du/dx = 0. So it goes from x = 0 to x = -1 to reach its maximum speed: the ke for each is the sum of the translational ke and the rotational ke. Clearly the one that is the slowest is the one which has the highest fraction of its energy as rotational ke.