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Answer:
21.4 mph
Explanation:
Circumference of tire in FEET = pi * d = pi * 1 ft = pi feet
pi feet x 600 rot/min * 60 min /hr * 1 mile / 5280 feet = 21.4 mph
When you are in free fall, the force of gravity is stronger than your velocity perpendicular to where you're falling, and you move at a constant speed downwards.
Under feelings of weightlessness, you are still being pulled by gravity, but your perpendicular velocity and distance from the source can cancel each other out.