Seat belts and air bags save lives by reducing the forces exerted on the driver and passengers in an automobile collision. cars are designed with a "crumple zone" in the front of the car. in the event of an impact, the passenger compartment decelerates with the car. by contrast, an unrestrained occupant keeps moving forward with no loss of speed (newton's first law! ) until hitting the dashboard or windshield, as we saw in figure 4.2. these are unyielding surfaces, and the unfortunate occupant then decelerates over a distance of only about 5 mm.
a. a 60 kg person is in a head-on collision. the car's speed at impact is 15 m/s.
estimate the net force on the person if he or she is wearing a seat belt and if the air
bag deploys.
b. estimate the net force that ultimately stops the person if he or she is not restrained
by a seat belt or air bag.
c. how does these two forces compare to the person's weight

To understand the behavior of the electric field at the surface of a conductor, and its relationship to surface charge on the conductor. a conductor is placed in an external electrostatic field. the external field is uniform before the conductor is placed within it. the conductor is completely isolated from any source of current or charge. part a: which of the following describes the electric field inside this conductor? it is in the same direction as the original external field.it is in the opposite direction from that of the original external field.it has a direction determined entirely by the charge on its surface.it is always zero. part b: the charge density inside the conductor is: 0non-zero; but uniformnon-zero; non-uniforminfinite part c: assume that at some point just outside the surface of the conductor, the electric field has magnitude e and is directed toward the surface of the conductor. what is the charge density η on the surface of the conductor at that point? express your answer in terms of e and ϵ0