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Surreal Ike
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I don't understand how walking 10 feet forward and then 10 feet back means you did zero work. If I pull a 1 pound weight 4 feet forward and 3 feet right, have I only done 5 foot-pounds of work?
Surreal Ike said:Force times distance, I suppose. But how can this idealized definition where you assume that you took the most efficient path ever be useful? My adding-the-distances definition would be more useful when you wanted to calculate the actual energy it would take to move something. When is the idealized definition ever useful?
Surreal Ike said:That still doesn't answer my question about the usefulness of work. Also, speed refers to the magnitude of the velocity vector, right? So why don't we have words that refer to the magnitude of the acceleration vector, the force vector, and the work vector?
Surreal Ike said:OK, so I'm beginning to get it now. Work equals force times distance. Force equals mass times acceleration, and acceleration equals velocity per second. Since velocity is a vector, that means that when you multiply it by a bunch of other numbers, it's still a vector.
That still doesn't answer my question about the usefulness of work. Also, speed refers to the magnitude of the velocity vector, right? So why don't we have words that refer to the magnitude of the acceleration vector, the force vector, and the work vector?
Also, isn't it terribly counterintuitive that hitting someone with a ball will exert a negative force on them? The ball starts decelerating as soon as it leaves your hand, right?
This is going off topic a little, but maybe the fundamental problem isn't the usefulness or integrity of these terms, but rather the very human tendency to borrow words from the common parlance to describe something precise and scientific. For instance, according to the scientific definition of "berry", blueberries, raspberries, blackberris, and strawberries are not "berries", while tomatos, avocados, eggplants, and chili peppers are. Makes you wonder why they didn't just come up with a new word. I think it's because making up new words like "blorf" makes you sound silly.
To Cyrus: I read about work in my math textbook, so I've got a good reason to believe what I said about work. If you want to criticize me for asking newbie physics questions in this forum full of geniuses, that's a far more valid criticism :-). Hope I'm not bothering you guys too much.
Surreal Ike said:Alright, thanks for the Wikipedia link. I now know that mechanical work refers to the magnitude of the work vector.
Surreal Ike said:Force times distance, I suppose. But how can this idealized definition where you assume that you took the most efficient path ever be useful? My adding-the-distances definition would be more useful when you wanted to calculate the actual energy it would take to move something. When is the idealized definition ever useful?
Surreal Ike said:I don't understand how walking 10 feet forward and then 10 feet back means you did zero work.
Work done over a distance is a measure of the amount of force applied to an object over a certain distance. It is calculated as the product of the force applied and the distance over which it is applied.
The units of work done over a distance are joules (J) in the International System of Units (SI). In other systems, it may be measured in foot-pounds (ft-lb) or kilogram-meters (kg-m).
Work done over a distance is directly related to energy. In fact, the unit of work (joules) is also the unit of energy. This is because work is the transfer of energy from one form to another.
To calculate work done over a distance, you need to know the force applied to an object and the distance over which it is applied. The formula is W = F x d, where W is work, F is force, and d is distance.
Yes, work done over a distance can be negative. This occurs when the direction of the force applied is opposite to the direction of the displacement. In this case, the work done is considered to be negative because the force is acting against the motion of the object.