00:01
Okay, so we're told that a pi -mason has an energy of 264 times the mass of the electron.
00:12
Oops, that should be m -pyon, not energy.
00:16
And we're told that, oops, the lifetime of its existence is equal to 8 .4 times 10 of the minus 17.
00:39
And so we can say that the uncertainty in the time is 8 .4 times 10 to the minus 17.
00:47
In general, you can use lifetimes in delta t synonymously or interchangeably, i should say.
00:54
And then our goal is to get the uncertainty and the mass of the particle.
01:04
And then we want to express it as a fraction of the particle's mass.
01:08
And so we want to use the uncertainty relation.
01:12
Delta e delta t is equal to h bar assuming that we're going to saturate the uncertainty we're going to be um the most certain that we can and so delta e e is m c squared so there's no uncertainty in c squared so that's going to be delta m times c squared times delta t and then so delta m is equal to therefore equal to h bar divided by delta t t, c squared, and then if we want to divide it by the actual mass, we're going to take that and say delta m over the mass of the pion is equal to h bar over delta t divided by c squared, and then the mass of the pion is equal to 264 times the mass of the electron.
02:23
And the mass of the electron, yeah, i guess that actually, that's it...