* It is important to have a clear idea of the system on which you are going to calculate the work, since work always involves a transfer of energy between two different systems. One system loses some energy, and the other one gains that energy.
What does the free-body force diagram look like for this system ?
* This part of the problem-solving process is the same as you used to solve dynamics problems involving Newton's Second Law.
What are the initial and final locations of the system ?
* Since non-zero work always involves movement, the system will have an initial and a final location. For problems involving kinetic energy, you will need to calculate (or find) the initial and final kinetic energies of the system.
* Identifying these two locations is useful in determining the displacement path of the system, since the path of the system is also the integration path for variables force,
What is the angle between each of the forces and the system's displacement ?
* Some forces may be perpendicular to the system's displacement and thus do no work. Only the component of a force that is parallel to the displacement will do any work.
* Resolve the forces into components that are parallel Fs and perpendicular to the system's movement.
Alternately you can also find the angle between a force and the system's displacement to calculate the work from
If F is constant.
What is the sign of the work done by each of the forces ? Is this reasonable ?
* If a force -- acting by itself -- will cause the system to speed up, then the force must do positive work. If a force -- acting by itself -- would cause the system to slow down or reverse direction, then its contribution to the net work must be negative.
* When the component of a force is in the same direction as the object's initial motion, then its work contribution will be positive. A force's contribution will be negative if it has a component of force that is opposite to the system's initial motion.
Is the force constant over the system's motion-path ?
* When the force is constant, the work done by that force is simply the component of the force along the path times the path-length, W = Fs s. Otherwise, you will have to determine the force's functional dependence along the path, F(s), so that you can integrate the force-distance integral,
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How can I apply the Work-Energy Theorem to analyze the problem ?
* Express the initial and final kinetic energies of the system in terms of the quantities given and the unknowns requested.
* Apply the Work-Energy Relationship, Wnet = KEf - KEo . Look at the resulting expression to see if you can solve for any unknowns.