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PHY303K-Spring07-Exam3-Moore

# PHY303K-Spring07-Exam3-Moore - midterm 03 SAENZ LORENZO Due...

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midterm 03 – SAENZ, LORENZO – Due: Apr 4 2007, 11:00 pm 2 W 1 = l 1 W r 1 = (5 m) (34 N) (9 m) = 18 . 8889 N . Apply summationdisplay vector τ = 0 about an axis through the point of suspension of the middle part of the mobile, we obtain l w W 2 r 2 [ W + W 1 ] = 0 W 2 = r 2 [ W + W 1 ] l w = (6 m) [(34 N) + (18 . 8889 N)] (5 m) = 63 . 4667 N . Apply summationdisplay vector τ = 0 about an axis through the point of suspension of the top part of the mobile, we obtain l e [ W + W 1 + W 2 ] r 3 W 3 = 0 W 3 = l 3 [ W + W 1 + W 2 ] r 3 = (5 m) (8 m) bracketleftBig (34 N) + (18 . 8889 N) + (63 . 4667 N) bracketrightBig = 72 . 7222 N . Question 3 part 1 of 3 10 points A beetle takes a joy ride on a pendulum. The string supporting the mass of the pendu- lum is 161 cm long. If the beetle rides through a swing of 28 , how far has he traveled along the path of the pendulum? 1. 73 . 7926 cm 2. 76 . 236 cm 3. 78 . 6795 cm correct 4. 81 . 1578 cm 5. 83 . 7758 cm 6. 86 . 3938 cm 7. 89 . 0816 cm 8. 91 . 8742 cm 9. 94 . 7714 cm 10. 97 . 7385 cm Explanation: Arc length is defined as s = r θ = (161 cm)(0 . 488692 rad) = 78 . 6795 cm , where theta is in radians. Dimensional analysis for θ cm · · π radians 180 = cm Question 4 part 2 of 3 10 points If the pendulum swings through the same angle 28 , what is the linear displacement experienced by the beetle? 1. 77 . 8989 cm correct 2. 80 . 5325 cm 3. 83 . 1066 cm 4. 85 . 9079 cm 5. 88 . 6128 cm 6. 91 . 4146 cm 7. 94 . 268 cm 8. 97 . 6494 cm 9. 100 . 74 cm 10. 103 . 95 cm Explanation: Using the law of cosines, we have bardbl vector R bardbl = radicalbig r 2 + r 2 2 r r cos θ = r radicalbig 2 (1 cos θ ) = (161 cm) radicalbig 2 [(1 cos(28 )] = 77 . 8989 cm .
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PHY303K-Spring07-Exam3-Moore - midterm 03 SAENZ LORENZO Due...

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