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Kinetic Energy with constant forces

The kinetic energy of a particle with mass and speed is somewhat mysteriously defined as
 (1.2)

This is true even in three dimensions but we'll start by considering it in just one dimension. We see now why this is a sensible definition.

If we apply a constant net force to an otherwise free particle it will accelerate with constant acceleration because . Remember that with constant acceleration we showed earlier that over some time interval you could relate initial velocity , final velocity , and distance traveled as

 (1.3)

Multiply both sides by , and this becomes . But in one dimension , the work done by the force F, so we end up with the simple looking formula

 (1.4)

This is called the work-energy theorem''. In words this says that the change in kinetic energy is equal to the work done by the force on mass . So this kinetic energy is a pretty neat thing. If you know its change, you can figure out how much work was done by all the forces acting on the the particle.

Next: Work with variable forces Up: Work Work Work Previous: Work with constant forces
Josh Deutsch 2003-02-02