Physics quiz question: magnitude of vector, given components

Physics 205A Quiz 3, fall semester 2011
Cuesta College, San Luis Obispo, CA

Of the three vectors P, Q, and R shown at right, the magnitude of vector R is:
(A) 3 units.
(B) 4 units.
(C) 5 units.
(D) 7 units.

Correct answer (highlight to unhide): (C)

The magnitude of vector R is the square root of the sum of the squares of its components R_x = +4 units, R_y = –3 units:

|R| = sqrt(R_x² + R_y²) = sqrt((+4 units)² + (–3 units)²)) = 5 units.

Response (D) is the arithmetic sum of 3 units + 4 units = 7 units.

Sections 70854, 70855
Exam code: quiz03Fn37
(A) : 1 student
(B) : 14 students
(C) : 32 students
(D) : 8 students

Success level: 58%
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00