The discussion revolves around the nature of the normal force experienced by a body inside an elevator, specifically whether it can be classified as a conservative force. Participants explore the implications of work done by the normal force during the ascent and descent of the elevator.
The conversation includes various interpretations of the normal force's behavior in relation to conservative forces. Some participants suggest that the normal force is not conservative based on specific examples, while others prompt further examination of the criteria for conservative forces.
There is an ongoing exploration of the definitions and criteria for conservative forces, with participants questioning assumptions about the normal force's work in different scenarios. The discussion reflects a mix of perspectives on the implications of kinetic energy changes during elevator motion.
Simply not true. When accelerating down the elevator exerts a normal force that is still "up" (not negative) and large enough so that your acceleration matches the elevator's acceleration. If that were not the case, you would either hit the roof or, even worse, fall through the floor.Caio Graco said:Consider a body inside an elevator. When it goes up and down, I believe that normal work (positive on the rise and negative on the descent).
Suppose that you step into the elevator on the 2nd floor. The elevator is at rest. Your kinetic energy is zero.Caio Graco said:Consider a body inside an elevator. When it goes up and down, I believe that normal work (positive on the rise and negative on the descent). My question is: since the total work on the closed path is zero, can we say that the normal force is conservative?
jbriggs444 said:Suppose that you step into the elevator on the 2nd floor. The elevator is at rest. Your kinetic energy is zero.
You press the button labelled "3" and rise to the third floor. The elevator stops here. You press the button labelled "1" (or "G"). The elevator proceeds downward past the 2nd floor without stopping.
At the moment that the elevator passes the second floor is your kinetic energy greater than, less than or equal to what it was when you first pressed the "3" button? At this moment, is is the total work that has been done on you by the elevator positive, negative or zero?
Yes.Caio Graco said:the normal force is not conservative because there is at least one case, like this, in which in a closed trajectory the total work is not zero