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SOLUTIONS TO EXERCISE 19
SOLUTIONS TO EXERCISE 19 The momentum of the comet is p = mv = 500 * 25 = 12500 ton km/s. The momentum of the planet is p = 5 billion * 0 = 0 ton km/s. The total momentum of the comet-plus-planet system is thus 12500 ton km/s. When the comet hits and sticks to the planet, the planet now has mass m = (5,000,000,500 tons). Because of Newton's First Law, the total momentum stays the same; so the planet must have p = 12500 ton km/s. Thus, since p = mv, v = p/m = (12500 ton km/s) / (5,000,000,500 ton) = 0.0000025 km/s = 0.0025 m/s. (This speed is, by the way, about 8 inches per day.) The direction of the motion is the direction the comet was travelling before the collision. |