http://www.ck12.org Chapter 8. Energy and Force
8.2 Key Concepts
- Work is simply how much energy was transferred from one system to another system. You can always find
the work doneonan object (or donebyan object) by determining how much energy has been transferred into
or out of the object through forces. If you graph force vs. distance, the area under the curve is work. (The
semantics take some getting used to: ifyoudo work onme,then you have lost energy, and I have gained
energy.) - Work can be computed by multiplying the distance traveled with the component of force that is parallel to that
distance - Energy can be transformed from one kind into the other; if the total energy at the end of the process appears to
be less than at the beginning, the “lost” energy has been transferred to another system, often by heat or sound
waves. - Work can be computed by multiplying the distance with the component of force that is parallel to the distance
- Efficiency is equal to the output energy divided by the input energy.
MEDIA
Click image to the left for more content.Math of Force, Energy, and Work
When an object moves in the direction of an applied force, we say that the force doesworkon the object. Note that
the force may be slowing the object down, speeding it up, maintaining its velocity — any number of things. In all
cases, the net work done is given by this formula:
W=~F·~d=~F·∆~x [1]Work is the dot product of force and displacement.In other words, if an object has traveled a distancedunder force~F, the work done on it will equal todmultiplied by
the component of~Falong the object’s path. Consider the following example of a block moving horizontally with a
force applied at some angle: