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Problem 1 a Muons are unstable particles which – if at rest in a laboratory – decay after a time of only 2.20 x 10-6 s. Suppose that a muon is created in a a collision between a cosmic ray and an oxygen nucleus at the top of the Earth's atmosphere, at an altitude of 20.0 km above sea level. (a) If the muon has a downward speed of 0.990c relative to the Earth, at what altitude will it decay? Ignore gravity in this calculation. (b) Without time dilation, at what altitude would the muon have decayed?