Chapter 4, Problem 64GP

If a car stops suddenly, you feel “thrown forward.” We’d like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there’s nothing for you to hold on to.

a. Draw a picture and identify all of the forces acting on you as the car travels in a straight line at a perfectly steady speed on level ground.

b. Draw your free-body diagram. Is there a net force on you? If so, in which direction?

c. Repeat parts a and b with the car slowing down.

d. Describe what happens to you as the car slows down.

e. Use Newton’s laws to explain why you seem to be “thrown forward” as the car stops. Is there really a force pushing you forward?