I really can't understand uncertainty

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The discussion centers on confusion regarding the concept of uncertainty in mathematical expressions. A specific example is presented: the multiplication of two numbers with uncertainties, questioning why the result is expressed as 4x5.2 +/- 0.5 x 0.2. Participants are encouraged to clarify how uncertainty operates in calculations and its implications. The thread emphasizes the importance of understanding uncertainty beyond just homework or coursework examples. Engaging in this topic is crucial for grasping fundamental mathematical principles.
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I really can't understand "uncertainty"

Hi guys,
I really can't understand "uncertainty"...
How it works, and Why it works
I don't understand..
Like why:
4+/-0.5 x 5.2+/- 0.2
=4x5.2 +/- 0.5 x 0.2?

Would anyone be kind enough to elaborate a bit for me?
Thanks for reading
 
Last edited by a moderator:
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Shing said:
Hi guys,
I really can't understand "uncertainty"...
How it works, and Why it works
I don't understand..
Like why:
4+/-0.5 x 5.2+/- 0.2
=4x5.2 +/- 0.5 x 0.2?

Would anyone be kind enough to elaborate a bit for me?
Thanks for reading

Why moved it here?
It is not homework, not coursework either That was just an example...
If any naive post will be moved, then who will ask questions here?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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