What is the danger in these situations?
If a person peels off a jacket or sweater while working at a computer, the computer can be destroyed. If a child slides down a plastic slide and then reaches for another person, the child can be in for a painful surprise. If an anesthesiologist does not wear the right type of shoes during surgery, the patient can be fatally injured. If a customer at a self-serve gas station slides back into the car while the tank is being filled, a fire can erupt at the pump nozzle when the customer returns to pull the nozzle from the car.
The answer is in this chapter.
One goal of physics is to identify basic forces in our world, such as the electric force we discussed in Chapter 21. A related goal is to determine whether a force is conservative—that is, whether a potential energy can be associated with it. The motivation for associating a potential energy with a force is that we can then apply the principle of the conservation of mechanical energy to closed systems involving the force. This extremely powerful principle allows us to calculate the results of experiments for which force calculations alone would be very difficult. Experimentally, physicists and engineers discovered that the electric force is conservative and thus has ...