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EXERCISE 29
Let's revisit our Harley-Davidson in Exercise 26. If I choose a cliff that's 1200 meters above sea level (about the height of parts of the Grand Canyon in Arizona), and push the Harley horizontally off the cliff: (a) How fast would the Harley have to be going in order for it to go into a stable orbit around Earth? (b) How fast would the Harley have to be going in order for it to escape Earth's gravity altogether and fly off into space? (c) Let's say I fail to achieve either of these speeds, and thus the Harley-Davidson falls to Earth, 1200 m below. How much gravitational force is Earth exerting on the Harley when it's one inch off the ground? (Remember that the Harley has a mass of 450 kg.) (d) How does the amount of force compare to the amount of force in Exercise 26, part (d)? Does the motorcycle, upon hitting the ground, suffer more, less, or equal damage here than the situation in Exercise 26, where it falls 80 meters? Please explain how the answers to these two two questions can both be correct, even though they may seem contradictory. |