key term - Nonconservative Forces

Definition

Nonconservative forces are forces that do not satisfy the work-energy theorem, meaning the work done by these forces depends on the path taken by the object, not just the initial and final positions. Unlike conservative forces, the work done by nonconservative forces is not equal to the change in potential energy.

5 Must Know Facts For Your Next Test

1. Nonconservative forces include friction, air resistance, tension forces, and forces that do work on a system over time, such as a constant applied force.
2. The work done by nonconservative forces depends on the path taken by the object, not just the initial and final positions.
3. Nonconservative forces can convert mechanical energy into other forms of energy, such as thermal energy, which is not recoverable.
4. The work-energy theorem does not hold for nonconservative forces, as the work done is not equal to the change in kinetic energy.
5. Nonconservative forces can cause energy dissipation, leading to a decrease in the total mechanical energy of a system.

Review Questions

• Explain how the work done by nonconservative forces differs from the work done by conservative forces.
  • The key difference is that the work done by nonconservative forces depends on the path taken by the object, not just the initial and final positions. This means the work done by nonconservative forces is not equal to the change in potential energy, unlike conservative forces. Nonconservative forces can convert mechanical energy into other forms, like thermal energy, which is not recoverable. This violates the work-energy theorem, as the work done is not equal to the change in kinetic energy.
• Describe the role of nonconservative forces in energy dissipation within a system.
  • Nonconservative forces, such as friction and air resistance, can cause energy dissipation within a system. As an object moves through a medium or interacts with a surface, nonconservative forces convert the object's mechanical energy into other forms, typically thermal energy. This results in a decrease in the total mechanical energy of the system over time. The work done by nonconservative forces is not stored as potential energy, but rather irreversibly converted into other forms, leading to a loss of usable energy within the system.
• Analyze how the presence of nonconservative forces impacts the application of the work-energy theorem.
  • $$W_{net} = \Delta K$$ The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy. However, in the presence of nonconservative forces, this theorem does not hold true. The work done by nonconservative forces is not equal to the change in kinetic energy, as these forces can also convert mechanical energy into other forms, such as thermal energy. This means the work-energy theorem cannot be directly applied to systems involving nonconservative forces, as the work done is path-dependent and not solely a function of the initial and final positions of the object.

Related terms

Conservative Forces:

Conservative forces are forces where the work done on an object depends only on the object's initial and final positions, not the path taken. The work done by conservative forces is equal to the negative change in potential energy.

Work:

Work is the transfer of energy due to the application of a force over a distance. It is calculated as the dot product of the force vector and the displacement vector.

Potential Energy:

Potential energy is the energy an object possesses due to its position or configuration. It is the energy stored in a system that can be released to do work.