The work-energy relation


Power of a force: Power in the ability of a force to do work



F: The force applied on particle Q

v: The velocity of Q


Example 1:


Note: The power of a force is related to the velocity of the particle it is acting upon.





Work of a force: The work U1-2 of a force on a particle over the interval of time from t1 to t2 is the integral of its power over this time interval.





Other methods to find the work of a force are:




Example 2:

Example 3:


Kinetic energy of a particle: A particle of mass m at each instant in time has a kinetic energy T given by


The work-energy relation: The relation between the work done on a particle by the forces which are applied on it and how its kinetic energy changes follows from Newton’s second law.


Note: The work done on a particle by the resultant force applied on it over a given interval of time will be equal to the change in kinetic energy of the particle. In other words, the kinetic energy of a particle is changed by an amount equal to the work which is done on the particle by the resultant force.


Example 4:

Example 5:



ã Mehrdad Negahban and the University of Nebraska, 1999-2002.

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Department of Engineering Mechanics, University of Nebraska, Lincoln, NE 68588-0526