## 20160904

### Physics quiz question: grains equivalent of an avoirdupois ounce

Physics 205A Quiz 1, fall semester 2016
Cuesta College, San Luis Obispo, CA

According to the National Institute of Standards and Technology[*], the avoirdupois ounce is defined to be exactly 16 drams, and one dram is defined to be exactly (875/32) grains. An avoirdupois ounce is equivalent to:
(A) 0.58514285714 grains.
(B) 1.708984375 grains.
(C) 437.5 grains.
(D) 448,000 grains.

Correct answer (highlight to unhide): (C)

Then setting up conversion factors such that unwanted units cancel (ounces, drams) while desired units remain (grains):

1 ounce = (1 ounce)·(16 drams/1 ounce)·((875/32 grains)/(1 dram)),

such that:

1 ounce = 437.5 grains.

Since all conversion factors are exact, then presumably this figure for the grains in an ounce is also exact.

Sections 70854, 70855, 73320
Exam code: quiz01bIR6
(A) : 1 students
(B) : 1 students
(C) : 55 students
(D) : 0 students

Success level: 96%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.10