Physics flashcard question: net force

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

Students were asked in the middle of their learning cycle the following think-pair-share question, to be answered using flashcards.

Two forces act on an object. The net force x-component on the object is:
(A) +3 N.
(B) +4 N.
(C) +5 N.
(D) +6 N.
(E) +7 N.
(F) +8 N.
(G) +11 N.
(H) (Unsure/guessing/lost/help!)

Sections 70854, 70855 (pre-)
(A) : 0 students
(B) : 5 students
(C) : 0 students
(D) : 0 students
(E) : 1 students
(F) : 16 students
(G) : 0 students
(H) : 13 students

This question was asked again after students were instructed to discuss with a neighbor how they chose their answer, and to convince each other why their answer is (in)correct.

Sections 70854, 70855 (post-)
(A) : 0 students
(B) : 4 students
(C) : 0 students
(D) : 0 students
(E) : 0 students
(F) : 20 students
(G) : 0 students
(H) : 14 students

Correct answer: (F)

Pre- to post- peer-interaction gains:
pre-interaction correct = 46%
post-interaction correct = 53%
Hake (normalized) gain <g> = 13%