LESSON 3: WORK, ENERGY AND POWER
Introduction
This lesson is devoted to the very important concepts of work and energy. These two quantities are
scalars and so have no direction associated with them, which often makes them easier to work with
than vectors. In this lesson, and the next we discuss an alternative analysis of the translational motion
of objects in terms of the quantities energy and momentum. The significance of energy is that they
are conserved. That is, in quite general circumstances they remain constant.
Learning Outcomes
After successful completion of this lesson, you should be able to:
1. Calculate the work done by an applied force that moves an object through a certain
displacement.
2. Distinguished between kinetic and potential energy.
3. Use the principle of conservation of energy to solve problems that involves moving objects.
4. Determine the power output of an energy source.
Discussion
3.1 Work
The term work, commonly used in connection with widely physical or mental activities, is restricted in
physics, in cases wherein there is a force and a displacement along the direction of the force.
In general, work is defined as the product of the displacement and the component of the force along
the displacement. Work is a scalar quantity.
If the force and the displacement are in the same direction, as shown in the diagram above, then the
work done by the force in moving the body is given by ,
