|
Consider all the forces you know of: gravity, normal, applied, friction, air resistance, tension, spring, etc. Ask: "Are any of these forces doing work upon the dart? Do any of these forces cause or hinder the displacement of the dart?" (Take your time and make sure you get this question right because the answer to the MOP question will depend upon it.) If any of the forces that you have identified as doing work are non-conservative forces, then you can be sure that the total mechanical energy is NOT conserved. On the other hand, if non-conservative forces are not doing work, then you can be sure that the total mechanical energy will be conserved - that is, remain constant. See Know the Law and Dictionary sections above.
|