Question about the significance of negative work

[Bipolarity]

I am having some trouble understanding the significance of negative work.

If the work that I do on object X is W, is it equivalent to saying that object X does work on me equal to -W ?

After all, work is scalar, so I can't fathom the physical significance of negative work.

Also, according to the work-kinetic energy theorem, due to the way in which work and kinetic energy are both defined, when I do work W on an object X, its kinetic energy increases by W and my energy decreases by W. Isn't that equivalent to saying that the object did work of -W on me, since at least in terms of kinetic energy the two are equivalent?

All help on my understanding of this concept is appreciated.

BiP

 

[Pengwuino]

Yes, what you stated is correct. The object does negative work on you. In a sense, the negative means that energy has been taken FROM the object in question (aka you). Remember, scalars can be negative! They just can't have direction. You might be confused because people in the early stages of physics courses will say that speed is a scalar and velocity is a vector, the former being unable to be positive, but this is specifically because of the way speed is defined; it is not a general property of scalars. I assume this is where the confusion lays?

 

[Bipolarity]

Yes, what you stated is correct. The object does negative work on you. In a sense, the negative means that energy has been taken FROM the object in question (aka you). Remember, scalars can be negative! They just can't have direction. You might be confused because people in the early stages of physics courses will say that speed is a scalar and velocity is a vector, the former being unable to be positive, but this is specifically because of the way speed is defined; it is not a general property of scalars. I assume this is where the confusion lays?

OK I get it so far. So if object A does work W on object B, then that is perfectly equivalent to saying that object B does work -W on object A?

BiP

 

[Crosstalk]

That is correct.

 

[PJC01]

olarBear,

Negative work is a concept that can be confusing, but it is an important concept in physics and has significant implications in various fields such as mechanics, thermodynamics, and electricity.

First of all, it is important to understand that negative work is not the same as "no work" or "zero work". Negative work occurs when the force applied to an object is in the opposite direction of its motion. This means that the work done by the force is actually taking away energy from the object, rather than adding to it. This can be seen in situations such as friction, where the force of friction opposes the motion of an object and causes it to lose energy.

In terms of your question about the equivalence of work done on an object and work done by an object, the answer is yes. As you correctly pointed out, work is a scalar quantity, meaning that it only has magnitude and no direction. Therefore, the work done on an object and the work done by an object are equal in magnitude, but have opposite signs. This is why when you do work on an object, its kinetic energy increases, but your energy decreases by the same amount.

In terms of physical significance, negative work is an important concept because it represents the energy transfer that occurs in a system. In situations where negative work is done, energy is being transferred from one form to another, or from one object to another. For example, when a car brakes, negative work is done by the brakes on the wheels, which results in the car losing kinetic energy and coming to a stop.

In summary, negative work is an important concept in physics that represents the energy transfer that occurs in a system. It is not the same as no work or zero work, and it has significant implications in various fields of science. I hope this helps clarify your understanding of this concept.