Physics quiz question: accelerating connected blocks

Physics 205A Quiz 3, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 4.125

Two blocks, of masses m_1 and m_2, are connected by a massless cord. (Note that m_1 < m_2.) The horizontal floor is frictionless. A constant applied force pulls horizontally on m_2, such that both blocks accelerate to the right. The magnitude of the net force on m_1 is __________ than the magnitude of the tension force between m_1 and m_2.
(A) greater than.
(B) equal to.
(C) less than.
(D) (Not enough information is given.)

Correct answer: (B)

The only horizontal force acting on m_1 is the tension force of m_2 on m_1, and thus it is equal to the magnitude of the net force on m_1.

Student responses
Section 72177
(A) : 2 students
(B) : 10 students
(C) : 2 students
(D) : 1 student

Success level: 66%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60