Physics quiz question: stress, strain on brick

Physics 205A Quiz 6, fall semester 2011
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 10.4

A load is to be supported by a brick placed in either of two orientations. To compress by 0.1 mm, __________ will require a greater force.
(A) brick (A).
(B) brick (B).
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

Hooke's law is given by:

(F/A) = Y·(∆L/L),

or:

F = Y·∆L·(A/L),

where Y and ∆L is the same for both bricks. The brick with orientation (A) has a larger cross-sectional area A that force is applied to, and also a shorter L along the direction that force is applied, such that it will require more force than the brick with orientation (B).

Sections 70854, 70855
Exam code: quiz06w4VE
(A) : 39 students
(B) : 8 students
(C) : 3 students
(D) : 2 students

Success level: 74%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.22