- #1
Misheel
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Homework Statement
The flag is d=2mm thick and D=30 m long. We roll the flag and stick the short side of the flag (long side is 30m, short side's length is not given) on the ceiling so that the flag unwraps back to the ground. Flag is M=30kg.
1. Find the time it takes to 10 m of the flag to get unwrapped (meaning 20 m is still in cylinder mode)
2. Find the acceleration at that given point in time.
p.s sorry for my bad English
Homework Equations
i guess :
D/M=p (linear density)
i am really not sure where to approach this problem.
The Attempt at a Solution
i assumed that the rolled flag is just like the piled up cylinders each ones radius is d=2mm lesser than the outside one. and assumed the most inner cylinder had r0=2mm radius. So to find the most outer radius of the rolled flag i used the arithmetic progress:
2*pi* (r0+r1+r2+r3+...rn)=30m
(r0+rn)/2*n=15/pi
n=(approx) 22.31 which has to be integer so -> 22 (?)
and the most outer radius wud be rn=44*10^(-3)m=4.4cm
and after this i have no clue where to approach this problem
mass is changing, radius is changing... don't know where to pick the point if to write a torque equation :P
any advice would be really helpful. Thank you