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Physics is owning me, can you help?

Nate1

All 4 wheels locked
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Gainesville/Tampa, FL
Year, Model & Trim Level
'96 FZJ-80
Right, so, I've been busy finishing my online physics homework, and I cannot get this problem for the life of me (which is annoying because I just finished the relativity and lorentz transformation assignments). If you are good at physics and think you know how to do it, please post your line of thoughts on the matter. I've tried obvious variations of the kinematic equations of oscillation that I can think of, but no dice.

The question is below:

A wheel of mass M = 4.5 kg and radius R = 0.90 m is free to rotate about its fixed axle. A spring, with spring constant k = 270 N/m, is attached to one of its spokes, a distance r = 0.33 m from the axle, as shown in the figure. What is the angular frequency of small oscillations of this system (in rad/s)?

prob211yw.gif





Thanks for any help!
 



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look at it from a different perspective.. this becomes a pendulum problem with a moment of inertia
 






I thought this was a torsional oscillator? :p I'm confused.
 






i agree with Izwack...make sure you take into account the difference in torque from r and R...
 






Nate1 said:
I thought this was a torsional oscillator?
I was thinking about that too but the spring is fixed somewhere on the wall. but looking at it from a torsional oscillator's perspective (also called a torsional pendulum), the first part would be finding kapa (torsional constant)
 






Ok, so if this is a pend problem I assume the axis cannot actually be the axle? It would seem to me there would only be two torques... the rotational inertia of the wheel (MR^2) and the spring. How would I calculate the torques cause by the spring though?

I thought I was to use the formula T = 2 pi * sqrt ( I / Mgd) but that obviously does not work in this case, since the wheel doesnt spin from gravity. I cannot figure out how to determine K the torque constant from the spring. I know angular freq = 2 pi / (T) but none the less, I only have one attempt to get this right, and I know that the way I was doing it was wrong ("practice" inputs).


Any more suggestions? I'm stumped.
 






Nate1 said:
Any more suggestions? I'm stumped.

change your major :p

in 4 years on art school i have never had to do anything like this :D :D :cool:
 






dman726749 said:
change your major :p

in 4 years on art school i have never had to do anything like this :D :D :cool:


And even if we did come across something like this Adobe and Macromedia would find out a way to solve it for us!! haha :D
 






I thought that was a plan for when of them there smoke grinders! :D
 






Physics scares me

Opened this up thinkin i *might* be able to help, but aparently i droped out long before i got to this kind of stuff...
 






I barely passed my way through high school and oddly enough honors physics was the only class i had an A in. Sorry, been too long- i cant help you. :p
 






Wow - you guys are all off...the coil springs, go this way. If they are attached to a spoke, you won't get near the suspension travel. And if they are attached to a wall....well I won't even comment on your welding capabilities. :rolleyes:

28933wheel.jpg
 






How would I calculate the torques cause by the spring though?

The torque caused by the coil spring (about the axle) is T=F*r, F is the force from the deflection of the spring F=k*X, so T=k*X*r.

You can relate X to r using trig. I could try to do this for you but my brain is old and tired. Eventually you should get an expression for the force by the coil spring in terms of the angle of oscillation.
 






:confused: :confused: :confused: :confused: :confused: :confused:
and still
:confused: :confused: :confused: :confused: :confused: :confused:
 






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