Physics quiz question: amount of mass attached to a spring

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

A mass is attached to a horizontal spring (with a spring constant of 
40 N/m), and has a 0.80 s period of oscillation. Neglect friction and drag. The mass attached to this spring is:
(A) 0.13 kg.
(B) 0.16 kg.
(C) 0.65 kg.
(D) 5.1 kg.

Correct answer (highlight to unhide): (C)

The period T of a mass m attached to a spring with spring strength constant k is given by:

T = 2·π·√(m/k),

such that the mass m will be:

T/(2·π) = √(m/k),

(T/(2·π))² = m/k,

k·(T/(2·π))² = m = 0.6484555753 kg,

or two significant figures, the mass attached to the spring is 0.65 kg.

(Response (A) is T/(2·π); response (B) is (2·π)/k; and response (D) is k·T/(2·π).)

Sections 70854, 70855
Exam code: quiz06co6O
(A) : 1 students
(B) : 4 students
(C) : 45 students
(D) : 2 students

Success level: 87%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.39