Cuesta College, San Luis Obispo, CA
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(A) 3.7 N.
(B) 0.92 N.
(C) 0.66 N.
(D) 1.8 N.
Correct answer (highlight to unhide): (A)
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ℓ = L·cos(60.0°).
The (clockwise) torque exerted by the string on the beam is then:
τ = T·ℓ,
such that the magnitude of the tension force T can be solved for:
T = τ/ℓ/ = τ/(L·cos(60.0°)),
T = (1.1 N·m)/((0.60 m)·cos(60.0°)) = 3.66666666... N,
or to two significant figures, the tension in the string is 3.7 N.
(Response (B) is τ/(2·L); response (C) is τ/2; and response (D) is τ/L.)
Sections 70854, 70855, 73320
Exam code: quiz05bL8D
(A) : 14 students
(B) : 2 students
(C) : 19 students
(D) : 30 students
Success level: 45%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.47
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