Dynamics question regarding moment of inertia

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This discussion centers on a dynamics problem involving the calculation of angular acceleration, frictional force, and acceleration of the center of mass (G) using the equations of motion. The user successfully calculated the friction force (ΔFf = 17.6N) and acceleration of G (Ag = 1.0281), but encountered an error in determining the angular acceleration (α), which was incorrectly calculated as 8.84 instead of the correct value of 0.295. The equations used include ƩFx, ƩFy, and ƩMG, with specific attention to the role of the cosine function in the torque calculation.

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chicagobears34
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Hi, I have a question regarding a dynamics question that be found here:http://by.genie.uottawa.ca/~mess/files/MCG_2107/MCG2107_M2005_p2.pdf, It is the first problem on that link (labeled number 2.)

I did ƩFx, ƩFy, ƩMG which allowed me to find angular acceleration, frictional force, and acceleration of G.
Friction force and acceleration of G were correct but angular acceleration was wrong.
My equations were:
ƩFx: -μkN + T cos(30)=maG
ƩFy: N-mg+Tsin(30)=0
ƩMG: Tcos(30)(0.075)-μkN(0.2)=Iα
ΔFf=17.6N, Ag=1.0281, α=8.84
α should be equal to .295
 
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hi chicagobears34! :smile:
chicagobears34 said:
ƩMG: Tcos(30)(0.075)-μkN(0.2)=Iα

why cos(30) ? :wink:
 
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