Cracking the SAT Physics Subject Test
CHAPTER 3 DRILL
- B Because the person is not accelerating, the net force he feels must be zero.
Therefore, the magnitude of the upward normal force from the floor must
balance that of the downward gravitational force. Although these two forces
have equal magnitudes, they do not form an action/reaction pair because they
both act on the same object (namely, the person). The forces in an
action/reaction pair always act on different objects.
- D First draw a free-body diagram.
