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Nonconservative Forces
by AudioLearn
of the gate, so to speak. At the end, the height comes into play because the car goes up a certain height against its potential energy. Solving for the velocity, you get 0.687 meters per second.
NONCONSERVATIVE FORCES
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Remember that forces can be conservative or nonconservative. A nonconservative force is one for which the work depends largely on the path taken. A good example of a nonconservative force is friction. Friction will depend on the path because, the longer the path, the more friction will become a force to be reckoned with. This means that there is no potential energy associated with nonconservative forces.
Work by a nonconservative force will add or take away the mechanical energy of a system. Friction is nonconservative because it creates thermal energy, which dissipates and ultimately removes energy from the system. Even if this type of energy can be retained, it cannot be completely converted back into work so it is not completely recoverable. Air resistance is also a nonconservative force. These energies and forces basically negate mechanical energy conservation idea.
So, what happens to the work-energy theorem when conservative and nonconservative forces act together. In such cases the net-work is the sum of the work by nonconservative forces plus the conservative forces. These, taken together, equal the change in kinetic energy of a system. For example, when pushing a box on an incline using an applied force, the vector goes up the incline while the force of friction goes down the incline. They oppose each other in a parallel direction. There is also the work done against gravity to consider.
Remember that the conservative work will equal the opposite of the potential energy. The nonconservative work will equal the change in kinetic energy plus the change in potential energy. This means that the nonconservative work adds to the mechanical energy of the system. If the nonconservative work is positive, then the mechanical energy increases, such as in pushing a crate up a ramp. If the nonconservative work is negative, the mechanical energy is decreased, such as when dropping an object that deforms on the ground. These equations are explained in figure 37:
