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EXERCISE 26
Earth's gravitational acceleration on any object at its surface is 9.8 meters per second squared. Astronomers often round this number off to 10 meters per second squared; it's close enough for most calculations. (a) A top-of-the-line Harley-Davidson can go from 0 to 75 mph in about four seconds on a dry racetrack. How does this vehicle's rate of acceleration compare to Earth's gravity? Remember to convert miles per hour into meters per second. (b) If you push this Harley horizontally off a cliff, how fast will it be going in four seconds? (c) How far will the Harley have fallen in four seconds? Remember that the acceleration of gravity is constant with time, so the Harley's average velocity is half the sum of the initial and final velocities. (d) Let's say the Harley hits the ground after falling for four seconds. If this Harley weighs 450 kg, how much gravitational force is Earth exerting on it when it's one inch off the ground? |