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?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Relativity Problem. I feel so stupid.

**Physics Forums | Science Articles, Homework Help, Discussion**