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SOLUTIONS TO EXERCISE 21
SOLUTIONS TO EXERCISE 21 The astronaut started moving with a momentum p = mv = 95 * 3.5 newtons. She ended her motion with a momentum 95 * 0.5 newtons in the opposite direction, or (95 * (-0.5)) newtons in the original direction. (a) The total change in momentum was thus the starting minus the ending momentum, or (95 * 3.5) - (95 * (-0.5) = 95 * 4 = 380 newtons. (b) For the thruster rocket to produce 380 newtons, it had to fire for 380 N -------- = 8.4 seconds. 45 N/s (c) Since F = ma, the acceleration a = F/m. So during that time, the astronaut's acceleration was (45 N) / (95 kg) = 0.47 m/s2. |