Calculate cangular momentum vector L

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AI Thread Summary
To calculate the angular momentum vector L, the equation L = mv X r is used, where m represents mass. The user is unsure of the value of m and is advised to leave it as a variable in the final answer. There is a discussion about the timing of the post affecting response rates, suggesting that posting during peak hours could yield quicker assistance. Additionally, it's noted that the question may not belong in the "Advanced Physics" forum. Overall, the conversation emphasizes the importance of including mass in calculations and the need for appropriate forum engagement.
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Homework Statement



calculate the angular momentum vector L

Homework Equations



r = rr(hat) r=√(xsquared + y squared) r(hat) = <cosθ, sinθ>
v = r(dot)r(hat) + rθ(dot)θ

The Attempt at a Solution


L = mv X r

I don't know m, how can i calcuate L? please help me
 
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welcome to pf!

hi classicphysic! welcome to pf! :smile:
classicphysic said:
L = mv X r

I don't know m, how can i calcuate L? please help me

yes, you do need m!

so just call it "m", and leave it in the answer :wink:​
 
i am waiting for the help people...checking it every hour but no body answers it
 
tiny-tim answered you already!

so just call it "m", and leave it in the answer

What more do you need?

And I really don't think this counts as "Advanced Physics". So, wrong forum?
 
hi classicphysic! :smile:
classicphysic said:
i am waiting for the help people...checking it every hour but no body answers it

posting it when the americans are about to go to bed, and the europeans are fast asleep :zzz:, isn't the best time, if you want a quick answer :wink:

(and posting it in the right forum would make it more likely that the right people see it)

btw, you don't need to keep checking … you should receive an email notification of each new post in any thread you've posted in :smile:
 
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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