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solution11 - fullwood(tf5349 QUIZ Rotation Catala(49033...

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fullwood (tf5349) – QUIZ Rotation – Catala – (49033) 1 This print-out should have 5 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points An electric motor rotating a workshop grind- ing wheel at a rate of 139 rev / min is switched off. Assume constant angular deceleration of magnitude 1 . 55 rad / s 2 . How long does it take for the grinding wheel to stop? Correct answer: 9 . 391 s. Explanation: Let : ω i = 139 rev / min and α = - 1 . 55 rad / s 2 . Since w f = 0, ω f = ω i + α Δ t = 0 Δ t = - ω i α = - 139 rev / min - 1 . 55 rad / s 2 parenleftbigg 2 π rad 1 rev parenrightbiggparenleftbigg 1 min 60 s parenrightbigg = 9 . 391 s . 002 (part 2 of 2) 10.0 points Through what angle has the wheel turned before it finally comes to rest? Correct answer: 68 . 3479 rad. Explanation: Since w f = 0, ω f 2 = ω i 2 + 2 α Δ θ = 0 Δ θ = - ω i 2 2 α = - (139 rev / min) 2 2 ( - 1 . 55 rad / s 2 ) parenleftbigg 2 π rad 1 rev parenrightbigg 2 × parenleftbigg 1 min 60 s parenrightbigg 2 = 68 . 3479 rad .
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