How fast must a pion be moving in order to travel 15 m before it decays?(adsbygoogle = window.adsbygoogle || []).push({});

The avg lifetime, at rest, is 2.6 x 10^-8 s.

The answer is supposed to be 0.89c

This sounds so easy. Like, just plugging in the formula but I'm not getting it. I haven't done relativity in so long. I think I must've forgotten more than I thought. I can't even find my notes now. Can someone please tell me how to get to the answer?

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# Relativity Problem. I feel so stupid.

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