posted by sarah .
Your friend is confused about ideas discussed in chapter 4 that seem to contradict ideas discussed in this chapter. For example, in Chapter 4 we learned that the net force is zero for a car traveling along a level road at constant velocity, and in this chapter we learned that work is done in such a case. Your friend asks, "How can work be done when the net force equals zero?" What is your explanation?
The work can be increasing the potential energy of the system, for instance, if an aircraft is flying vertically at constant speed, the net force is zero, but the PE of the aircraft is increasing.
e car goes once around the track in 361 s. What is the magnitude of the centripetal acceleration of the car?