Focus of this lesson. Distinguishing Force and Energy

[Bernard NebelKeymaster]

Force and energy are commonly confused, and that confusion can lead to many misconceptions. The focus of this lesson is to clarify the distinction between force and energy. To be sure, force and energy are commonly interconnected.

For example, the release of potential energy in gasoline powers the engine that accelerates a car from a zero to sixty miles per hour in 60 seconds. In previous lessons (C-1 and C-3) we have looked at this in terms of energy–a conversion of potential energy in fuel to movement energy of the car.

However, we can focus in on the “push”– How hard do we have to push on the car to accelerate it the same amount? Such a push can be measured. (Have students consider how.) Simply put a scale between the car and the “pusher” and read the strength of the push in pounds. This push is known as force, and it can be measured in pounds. Note how the idea of force omits energy from consideration. It is simply a push measured in pounds.

Students will recognize and be familiar with pounds in terms of weight. Yes, it is exactly the same thing. Gravity is a natural force (no energy is involved) that pulls everything toward the center of the Earth. Standing on the floor, you are pushing down on the floor with a force of _______ pounds equal to your weight. (Force is also commonly measured in units called newtons: one pound equals about 4.5 newtons; one newton equals 0.22 pounds.)

Another natural force is magnetic force, the force observed by two magnets pulling (or pushing) on one another. Again the pull/push can be measured in pounds or newtons. One readily observes that the force of the pull/push between two magnets drops off rapidly with distance. Gravity also drops off with distance from the center of the Earth although one doesn’t notice it so much. However, you will weigh slightly less on the top of a mountain than you do at sea level. (There are two other natural forces involving the nature of atoms, but these can be neglected for the present.)

Please post questions or comments.

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