How do nonconservative forces affect work done in a round trip?

In summary, the conversation revolves around a question in a textbook regarding the work done by a resistive force during a round trip bicycle ride. The individual initially calculates the work to be -30J, but the book states the answer as -30000J. It is later revealed that the discrepancy is due to a units problem, with the correct calculation being -30,000J.
  • #1
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2
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Hi!

I've been needing help with a question in my textbook. It seems so stupidly easy, but I can't get it. (Ironically enough, I understood all the others).. here's the question:

A bicyclist rides 5.0km due east, while the resistive foce from the air has a magnitude of 3.0N and points due west. The rider then turns around and rides 5.0km due west, back to her starting point. The resistive force from the air on the return trip has a magnitude of 3.0 N and points due east. Find the work done by the resisitve force during the round trip.

Here's what I did:
W = Fd
W = (3.0N)(5.0km) = -15J
since its a round trip, I doubled it and get -30J, but the book says that the answer is -30000J

Any help would be greatly appreciated!
 
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  • #2
You have a "units" problem. A "Joule" is defined as the work done by a force of 1 Newton acting over a distance of 1 meter- not 1 kilometer.

How much work is done by a force of 3 N acting over a (total) distance of 1000 m?
 
  • #3
oh.. a UNITS problem.. I feel very stupid.. sorry for bothering you with that, but thanks! :)
 

What are nonconservative forces?

Nonconservative forces are forces that do not conserve mechanical energy. This means that the work done by these forces is dependent on the path taken and not just the initial and final positions of the object.

What are some examples of nonconservative forces?

Some examples of nonconservative forces include friction, air resistance, and tension in a rope. These forces result in the dissipation of mechanical energy and can cause objects to lose kinetic energy and slow down.

How do nonconservative forces affect the motion of an object?

Nonconservative forces can either increase or decrease the kinetic energy of an object, depending on the direction and magnitude of the force. These forces also result in a change in the total mechanical energy of the system, as some energy is converted to other forms, such as heat.

Can nonconservative forces do work on an object?

Yes, nonconservative forces can do work on an object. However, the work done by these forces is not path-independent, meaning that the work done depends on the path taken by the object.

How can we account for nonconservative forces in calculations?

To account for nonconservative forces in calculations, we can use the concept of potential energy. Nonconservative forces are often associated with a potential energy function, which takes into account the work done by these forces and their effect on the total mechanical energy of the system.

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