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Moun Halflife question

Can anyone help me with this? Q

The half-life of a moun at rest is 1.5x10^-6s
show that about 0.0001% of the mouns formed high in the atmosphere would remain after travelling 9x10^3m.
(ignoring relativistic factors)

Reply 1

Eimmanuel

Study Forum Helper

Original post by joyoustele

Do you mean moun or muon?

I think there is missing info. You need to know how fast the particle (moun or muon) is travelling for a distance of 9 × 10³ m.

Reply 2

phys981

Original post by Eimmanuel

Do you mean moun or muon?

I think there is missing info. You need to know how fast the particle (moun or muon) is travelling for a distance of 9 × 10³ m.

I think you can do this with no more info IF you assume the muon is travelling at approx the speed of light.

(1) Work out how long it will take to travel 9 x 10³ m

(2) Work out how many half lives this is.

(3) Do your half life magic (and remember they've asked for the % so your answer will initially look smaller than that given).

Reply 3

Eimmanuel

Study Forum Helper

Original post by phys981

I think you can do this with no more info IF you assume the muon is travelling at approx the speed of light.
...

Let me put it in this way. I would avoid writing such phrase "assume the muon is travelling at approx the speed of light" in reply to students question especially concerning calculation.

If this is to undergraduate students, I believe it is ok but to GCSE or A level students, I will avoid it if I am aware of it. Why?

The phrase “assume the muon is travelling at approx the speed of light” can be confusing for the weaker or average students. They would wonder should they use 0.9c, 0.99c, 0.999c or other values if they do not encounter such phrase before.

This is why I would rather NOT assume that they know it and say there is missing info, unless the question explicitly states such assumption (muon is travelling at approx the speed of light).

I am speaking from experiences.

Reply 4

phys981

Original post by Eimmanuel

I am speaking from experiences.

I bow to your superior experience :wink:

But above is how I'd do it with my own students.

Reply 5

joyoustele

Original post by Eimmanuel

Do you mean moun or muon?

I think there is missing info. You need to know how fast the particle (moun or muon) is travelling for a distance of 9 × 10³ m.

I did the question :smile:

Thanks, There was a missing information that I hadnt realised