The return stroke of a bolt of  lighting can travel at a speed of 87,000 miles per second.[Almost half the speed of light.] At this speed,how many times can an object travel around the World in one.[see exercise 52]

52) Find how much rope is needed to wrap around the earth at the equator, if the radius of the earth is 4,000 miles. [hint:use 3.14 for π and the formula for circumference.]


C=2 πr

C=2 π4,000

C=8,000 π


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