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Home Minds On Work and Energy Mission WE9 Work and Energy Conversions Help Help 3

Mission WE9 Work and Energy Conversions

The Question

Some forces are categorized as conservative forces (or internal forces) while others are categorized as non-conservative forces (or external forces). Which of the following forces are generally categorized as non-conservative (or external) forces?

Define Help

Definition of Conservative Force:
All the different types of forces that could do work upon an object can be categorized as either conservative or non-conservative forces. A conservative force is a type of force that serves to transform an object's energy between kinetic and potential. When only conservative forces do work upon an object, the energy of the object changes forms (KE to PE or vice versa) without changing the total amount of mechanical energy. Mechanical energy is said to be conserved.



 Definition of Non-conservative Force:
All the different types of forces that could do work upon an object can be categorized as either conservative or non-conservative forces. A non-conservative force is a type of force that changes the total amount of mechanical energy possessed by an object. When non-conservative forces do work upon an object, the total amount of mechanical energy changes. Mechanical energy is not conserved.

Think About It

There are two forces commonly discussed in MOP questions that serve as conservative forces - gravity and spring. The force of gravity, when it does work, serves to change gravitational potential energy into kinetic energy or vice versa. The spring force, when it does work, serves to change elastic potential energy into kinetic energy or vice versa. All other forces are regarded as non-conservative forces that serve to change the total amount of mechanical energy in one of its two forms.

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