Difference Between Work And Force
The Meaning of Work
In everyday conversation, the word “work” has various meanings. For example, look at these three sentences:
1. It’s time to work on the lawn.
2. You will need paper and pencil to work out this problem.
3. I fixed the clock and want to see if it will work.
In each of these sentences, “work” is used in a different way and has a different meaning. To a scientist, however, the word has a very precise meaning. In scientific use, “work” is not concerned with how much effort is expended in doing something. To a scientist, work is done only if a push or a pull on an object causes it to move in the direction of the push or the pull. This scientific definition of work was devised in 1829 by the French mathematician Gaspard Gustave de Coriolis. According to this definition, Atlas did no work by merely holding the Earth in place. He would have worked only if he had moved the Earth about while pushing or pulling it.
The Meaning of Force
Instead of speaking about a push and a pull, it is better to use the word “force.” You exert a pushing force on the pedals of a bicycle when you ride it uphill or on level ground. (Actually, you push downward on the pedals, but the chain and gears of the bicycle change this push to a force that acts along the road.) You apply a pulling force on the rope tied to a sled as you move it to the top of a snowy hill. In each of these instances, you do work because the force you exert causes the object—the bicycle or sled—to move in the direction of the force. Suppose you load the sled with firewood to the point where you cannot move it at all. Then you do no work, even though your effort to pull the sled causes you to become exhausted.
What You Work Against
If you apply a steady force to a door at the right place and in the right direction, the door will open. But if the door is already open and you lean against the air instead, you will fall through the doorway. One of the first things you learned as a child was that you could not push on something that was not there. In other words, a force cannot be exerted on an object unless the object somehow opposes, or resists, it. You can apply a steady force to the pedals of a bicycle to keep it moving only because something is resisting the force. The bicycle resists being kept in motion.