Question about Energy/Work

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In summary, energy is the ability to do work. Work is a force times a distance. If there is no movement, then the energy is just heating up the muscles.
  • #1
I'm a little confused about what exactly work/energy is. I understand that if I exert 10 N o a box over a distance of 10 m, 100 J of energy are expended. However, say I exert 10 N on a 100 kg box, and it does not move, why is no energy expended? Such an action certainly requires energy?
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  • #2
Energy is transferred in the form of chemical reactions in your body that fuel your exerting of force. However, no work is done on the 100-kg box due to the fact that there is no movement. The force of static friction counteracts the force you exert.
  • #3
First, realize that physicists have a very specific mathematical meaning of "work" and "energy" and they are not the same as "effort".

You should meditate on the case of a table. A table can hold things up indefinitely without expending any energy at all. No energy is required, because while the table is pushing up on the object, the object isn't moving, so no work is being done.

It may be tiring to hold the same object stationary in your outstretched palm, but that doesn't mean that your palm is doing work *on the object,* any more than the table is doing work on the object when it supports the object. You get tired because the biology of your muscles is such that they need to burn fuel just to create a force in the first place.

If the object doesn't move, your muscles burn chemical fuel, releasing energy, but that energy just ends up heating up your muscles instead of doing work on the object.
  • #4
Energy is the ability, the potential do do work, rather than actually doing work. So an electromagnmetic field, for example, contains energy, but it might just sit there without doing any work.

Work is defined as a force times a distance. So in general energy has the ability to exert such a force, but unless something is moved it does not fit the definition. You can push, for example, as hard as you like against a wall but unless it moves the definition says no work has been done. But as noted above, you HAVE expended energy trying to push it.

A closely related concept is expended per unit time...So if you perform some movement,some work, like accelerating a car, the faster you do it the more POWER is expended. These definitions take some time to get used to, sort of like the distinction between 'affect' and 'effect'...

1. What is the difference between energy and work?

Energy is a measure of the ability to do work, while work is the transfer of energy from one object to another. In simpler terms, energy is the potential to do work, while work is the actual process of using that energy.

2. How is energy converted into work?

Energy can be converted into work through various forms, such as mechanical, electrical, thermal, or chemical energy. The specific conversion process depends on the type of energy and the system in which it is being used.

3. Why is energy important in our daily lives?

Energy is essential for our daily lives because it allows us to perform various tasks, such as cooking, transportation, and powering our devices. Without energy, our modern society would not function as it does today.

4. What are the different forms of energy?

There are several types of energy, including kinetic, potential, thermal, chemical, nuclear, and electromagnetic energy. Each type has its own unique characteristics and applications.

5. How is work related to the conservation of energy?

The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted from one form to another. Work is a form of energy transfer, and therefore, it follows the same principle of energy conservation.

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