Physics quiz question: Swatch Internet Time beats

Physics 205A Quiz 1, fall semester 2019
Cuesta College, San Luis Obispo, CA

Swatch Internet Time was proposed in 1988, where 1 day is divided into 1,000 "beats."[*] A day is defined to be 24 hours, an hour is defined to be 60 minutes, and a minute is defined to be 60 seconds. The duration of 1 beat is:
(A) 3.6 s.
(B) 86.4 s.
(C) 1.5×10⁵ s.
(D) 8.64×10⁷ s.

[*] swatch.com/en_us/internet-time#main.

Correct answer (highlight to unhide): (B)

The duration of a beat in seconds can be determined by setting up conversion factors such that unwanted units cancel (beats, days, hours, minutes) while desired units remain (seconds):

1 beat = (1 beat)·((1 d)/(1,000 beats))·((24 h)/(1 d))·((60 min)/(1 h))·((60 s)/(1 min)),

1 beat = (1 beat)·((1 d)/(1,000 beats))·((24 h)/(1 d))·((60 min)/(1 h))·((60 s)/(1 min)/),

1 beat = 86.4 seconds.

(Note that all of the factors in this calculation are exact definitions or conversion factors.)

(Response (A) is ((1/1000)·60·60; response (C) is (1000)·(1/24)·60·60; response (D) is (1000)·24·60·60.)

Sections 70854, 70855
Exam code: quiz01B34t
(A) : 3 students
(B) : 46 students
(C) : 4 students
(D) : 1 student

Success level: 84%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.42