- #36
Femme_physics
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Femme_physics said:Good morning ILS :)
And damn it I knew I forgot something. I got used to the inclined coordinates. Add Fs sin(30) in sum of all forces on y.
Can you check if the y component of Fs is up or down?
That is, can you check the sign of "Fs sin 30"?
Femme_physics said:But it can't be wrong, I already drew flowers and butterflies. It can't. Flowers and butterflies means I'm right. Sorry, it's a cosmological fact. Whatever you think about mechanics is wrong because of that.
Okay, fine, I'll fix the sign and get the right figure, but that's it basically, that is the answer right? I'll have to do some reverse engineering after I'm done to better follow what you've been trying to tell me.
Femme_physics said:Then how come I'm not considering moment of inertia, friction, etc, or whatever in my calculations of centripetal force? Shouldn't it matter if those are the things that REALLY cause centripetal force?
In kinematics/dynamics, we ignore friction by saying "smooth surface" and ignore moment of inertia by saying "point mass". I'm curious why aren't we told anything in questions about moment of inertia and friction if it so heavily affects the score. What if there was no friction, indeed? Would there be no centripetal force/much much lesser to an insignificant level?
Well you do consider all forces that act on the block (weight,normal,friction). But some of those forces do not have components in the radial direction such as weight. If you were to have no friction than the centripetal force is supplied purely by the component of the normal force that is in the radial direction.
The moment of inertial does not come into play unless the block is accelerating in a circle. Because just like F=ma, M=I(alpha) where 'M' is the net moment or torque, 'I' the moment of inertia, and 'alpha' the angular acceleration. Since you have no angular acceleration in this problem there is no torque applied to the block and no need to worry about the moment of inertia...
Femme_physics said:Will this calculation FINALLY lead to my answer?
http://img718.imageshack.us/img718/9376/fxfxfxfxfxfxfxfx.jpg
Hey! Not so fast!Femme_physics said:Why but of course I did!
*sneaky shifty look*
Thank you ILS, and thank you everyone for helping me through this! :)
Femme_physics said:Sorry for the delay, but I always get the job done! ...eventually. :)
Is this the final equation I need to solve, then?
Femme_physics said:Score! :) Thank you ILS, Everyone. Long overdue!