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SOLUTIONS TO EXERCISE 20
SOLUTIONS TO EXERCISE 20 The first mini-asteroid has a momentum p = mv = 15 * 15 = 225 kg m/s east. The second mini-asteroid has p = mv = 15 * 30 = 450 kg m/s west, or -450 kg m/s east (the negative is important, because direction matters). (a) According to Newton's First Law, the combined momentum of the two mini- asteroids will be the same before the collision as after the collision. Thus, total p = 225 + (-450) = -225 kg m/s east. total m = 15 + 15 = 30 kg. So since p = mv, v = P/m = -225 / 30 = -7.5 m/s east, or 7.5 m/s west. (b) From part (a) above, the total p = -225 kg m/s east. One of the asteroids now has momentum p = mv = 15 * 25 = 375 kg m/s west, or -375 kg m/s east. Thus, the other asteroid now has p = (-225) - (-375) = 150 kg m/s east. That asteroid is thus moving at v = P/m = 150 / 15 = 10 m/s east. |