20150716

Physics quiz question: magnitude of vector, given components

Physics 205A Quiz 3, fall semester 2013
Cuesta College, San Luis Obispo, CA

A vector R has x- and y-components as shown at right. The magnitude of vector R is:
(A) 1.9 m.
(B) 2.6 m.
(C) 7.0 m.
(D) 12 m.

Correct answer (highlight to unhide): (B)

The magnitude of vector R is the square root of the sum of the squares of its components Rx = +1.1 m, Ry = –2.4 m:

| R| = sqrt(Rx2 + Ry2) = sqrt((+1.1 m)2 + (–2.4 m)2)) = 2.640075756 m,

which to two significant figures is 2.6 m.

Response (A) sqrt(|Rx| + |Ry|); response (C) is (Rx2 + Ry2); response (D) is (|Rx| + |Ry|)2.

Sections 70854, 70855, 73320
Exam code: quiz03eL3v
(A) : 3 students
(B) : 65 students
(C) : 2 students
(D) : 0 students

Success level: 93%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.13

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