Forces 33
that causes a change in velocity. The second law then tells how big the effect of the
force is. Let us look at a familiar situation to get a better understanding of the rst
and second laws.
4.7.1 WHAT AND WHERE IS THE FORCE?
When riding in a car and going into a circular turn, think about what you experience.
What you will probably say is that you feel a force pulling your shoulders toward the
outside of the turn. Let us analyze this carefully. If there is indeed a force pulling on you
outward, then what is its cause? In other words, what is the physical agent producing the
force? After all, since we have de ned force as the interaction between two objects, then
what is the other object producing the outward force on you? For insta ...