the two question are similar, but when they cacluating the angular acceleration,
ID: 2087153 • Letter: T
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the two question are similar, but when they cacluating the angular acceleration, a=? * r. the first question use the outer radius, the second question use the inner radius. I just don't know which radius should i use
17-96. The spool has a mass of 100 kg and a radius of gyration of kg = 0.3 m. If the coefficients of static and kinetic friction at A are n = 0.2 and is = 0.15, respectively, determine the angular acceleration of the spool if P = 50 N. 250 mm 100(98)N SOLUTION +EF, - mag) : 50 + FA = 100 g +T EF, = m(acy: NA - 100(9.81) = 0 C+XMg = Ica: 50(0.25) - F.(0.4) = [100(0.3)”lar Assume no slipping: 0g = 0.4a a = 1.30 rad/s ag = 0.520 m/s2 NA - 981 N F , = 2.00 N Since (F 1)max = 0.2(981) - 196.2 N > 2.00 N E RRSON Lo 5mExplanation / Answer
The value of radius must be chosen as per the FBD, you are solving. And it doesn't matter what r you are choosing, as the angular acceleration will be same for r2 and r1, as both radius have a common centre. So feel free to choose any r1 or r2. But also take care for the equation, there will be change in the term (ms* r1 *alpha) accordingly.
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