Interesting Links (example problem):
Work and energy are terms that have technical meanings that are more precise than those that people commonly use. Work is done only when there is a force that causes the object to move through a displacement. Work is not done, for example, when you merely hold a weight at arm's length for 3 hours (if you could). We will discuss energy later, but for now, the work done by friction is lost to heat - this is the "energy lost due to friction" requested in problem 11, page 194.
When the force is constant, the work done is the magnitude of the displacement times the component of the force in the direction of the displacement:
The angle is measured from the direction of the force to the direction of the displacement. Angles from zero to 180o are possible.
Work is a scalar; that will be obvious from the definition that will be given in the next mini-lecture. Its units are newtons times meters, for which we use the name joules (J). These are the same units as torque, but joules are never used for torque! Besides, torque is a vector.
Example 1: Block on a rough plane
Example 2: Two blocks connected by a cord
Here are a few additional problems for which I have not supplied the answers. If you want the answers, post a request in the Question Area for this module.