# Motion of muon

1. Jun 14, 2007

### say_physics04

1. The problem statement, all variables and given/known data
a muon moving in a straight line enters a region w/ speed of 5 x 10^6 m/s. it then slowed down at a rate of 1.25 m/s^2. how far does the muon take to stop??

2. Relevant equations
2ad + square of initial velocity = square of final velocity

3. The attempt at a solution
my answer was 1 x 10 ^13 m....
i substituted the given (acceleration, initial velocity, and the final velocity which is 0) to the equation, then i got that displacement...

my prof told me that the answer must be 0.1 m,,
i don't know why,,, is it something about the behavior of muon??
or if isn't,, is there something wrong in the given??

thx ,,, i really need this asap... thx again!

Last edited: Jun 14, 2007
2. Jun 14, 2007

### malawi_glenn

have you calculated relativistic + that a muon has a certain life time? (apply time dilation)

3. Jun 14, 2007

### say_physics04

what is the exact life span of a muon??
thanks.. i'll try the relativistic effects but im not sure about the life span of the muon...

4. Jun 14, 2007

### malawi_glenn

you can find by googling hehe

5. Jun 14, 2007

### say_physics04

hahaha... thanks, but i want to know the "rightest" answer because there will be a possibility that I'll find "different" lifespans..
thanks

6. Jun 14, 2007

### malawi_glenn

but all muons do not live exactly the same dude..
the "lifetime" is on average how long time a muon will live before decay..

Have you tried google it? How do you know that you will get different? If you look it up in books, you will get different values there too..

Also what kind of course is this, particle physics? special relativity, or?
this is why "2. Relevant equations" is there, so we who helps know what kind of course it could be.

but when applying the life time of muon, we need to know how far it had traveled before it enters the target.

7. Jun 14, 2007

### say_physics04

i've used the 2.2 microseconds lifespan... i always get 11m displacement..
pls help me to get an answer closer to 0.1m

anyways. this is just mechanics, i want to know why my prof's answer is 0.1m
i'm afraid i'm running out of time,, i really need this asap...
thanks for ur answers! pls help me further....

8. Jun 14, 2007

### Dick

Your original solution is the correct solution to the problem. It says how long to 'stop' the muon. I don't think 'decay' and 'stop' mean the same thing. I would stand your ground with the original solution.

9. Jun 15, 2007

### say_physics04

hmm,, thanks to all!!!
i just got home from school...
and u know what?? there's something wrong at the given!! the acceleration is not that low... my prof's mistake!
thanks again