When two blocks slide together across a frictionless surface
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
When two blocks slide together across a frictionless surface, the force that each block exerts on the other is not included in the net force used to determine their common acceleration. Which of the following best explains why?
(a) The contact forces act in opposite directions on the two blocks and cancel when the blocks are treated as a single system.
(b) Because the surface is frictionless, any forces parallel to the surface—including the contact force—must be zero.
(c) The contact force is perpendicular to the direction of motion, so it has no effect on the blocks’ acceleration.
(d) The applied force simply passes through both blocks without being altered, so the contact force does not influence how they speed up.