# physics

posted by carolyn

Lunar astronauts placed a reflector on the Moon’s surface, off which a laser beam is periodically reflected. The distance to the Moon is calculated from the round trip time. The taken for the laser pulse to travel there and back again can be measured to 0.1 ns. What percent accuracy is this, given the average distance to the Moon is 3.84 X 108 m?

1. Damon

.1 ns = 1 * 10^-10 m/s
c = 3*10^8 m/s approx

d = 2 * 3.84 * 10^8 = 7.68 *10^8 m
time = d/c = 7.68/3 = 2.56 s

percent = (10^-10/2.56) * 100
= 10^-8/2.56
= 10 * 10^-9 /2.56
= 3.9 * 10^-9 percent

2. Turki

99.99% of accuracy

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