Ch 5 Work and Energy Introduction


Be sure to check out the Physics Classroom BIG Ideas on Work! Physics Classroom Calculating Work

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Work and energy enjoy a very close relationship. Energy is defined as the 'ability to do work'. Work is defined in mechanics in terms of forces acting on
objects to move the object through a distance.

In Chapter 5 we will look closely at work done against friction, gravitational potential energy & work, kinetic energy & work, and spring energy. All work
is related to the transfer and/or transformation of energy.

Work = Force X distance

but the force in the equation is the portion of a force acting in the plane of motion!


Work and energy are SCALAR quantities unlike force. The direction of work and energy does not matter at all.
Work is typically done against friction or gravity, but can also be done as part of an energy transformation such as stretching a spring, compressing a gas,
or a variety of other situations that we will explore further in the 2nd semester of physics.

Law of Conservation of Energy

Energy is neither created nor destroyed. Energy is transferred or transformed.

One thing to keep in mind about energy transformations is that energy 'lost' to friction turns into thermal energy that is considered low quality because
it is almost never useful energy after the process. The thermal energy is usually dissipated to the environment.

Kinetic energy is energy associated with motion. Whether we re thinking about a speeding truck r bullet or the microscopic vibrations of atoms in their lattices
due to temperature... MOTION is the key!
Kinetic energy of gas molecules
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Roller coaster energy exchanges between PE and KE
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