- #1
Noctix
- 9
- 0
Homework Statement
A 1.0- kg mass is attached to a string wrapped around a shaft of negligible mass and having a 6.0cm radius. A dumbbell-shaped "flywheel" made from two 0.500- kg masses is attached to one end of the shaft and perpendicular to its axis. The mass attached to the string is released from rest and allowed to fall 1m to the floor. It reaches a speed of 2.68 m/s just before striking the floor. How far apart are the masses of the dumbbell?
Homework Equations
(between dumbells) I=mr2
m1=flywheel
m2=weight
The Attempt at a Solution
KE(flywheel) + KE(weight)=PE(flywheel)+PE(weight)
the height of the flywheel is 0(right?), so i can take out PE(flywheel).
then I set up 1/2Iw2 + 1/2m2v2 =m2gh
i then change 1/2IW2 to 1/2mr2v2/r2 which then becomes 1/2m1v2
i feel like something is really wrong here because my radius's cancel and those are what I'm solving for. also, i never used the given radius of the shaft, so i think I'm missing something there too. Do I have to include some kind of kinetic moment of inertia equation for the weightless shaft(i didn't think so because m=0...or maybe i just ignore m)? also, do i need the regular kinetic energy 1/2mv2 of the dumbells along with their other kinetic energy 1/2Iw2??
Thank you a thousand times in advance for the help, it's greatly appreciated.
Last edited: