Kinetic and Potential Energy

Kinetic energy refers to the amount of energy a moving object has.  The greater the mass and the greater the kinetic energy. 

The formula for kinetic energy is:

The units of energy are Joules (J).  It is a scalar, not a vector quantity.

This also means that the faster an object travels, the amount of energy will increase exponentially. This is one of the many reasons that we have low speed zones on certain areas such as school.

Similarly, the more massive an object is, the more kinetic energy it has if it is travelling at the same velocity as a smaller one. 



Another concept you need to be aware of is the idea of work.  Work is done when a force is applied to move an object a certain distance.  So for our friend below , he has to overcome friction to get the box to move.  He will also have to push it the entire distance it has to move.  The formula for work is:

Not only does work involve moving objects, but also with moving ones.  You should be aware that a force will cause an object to undergo acceleration.

As a result, the force applied over a certain distance will result in a change in kinetic energy.  Thus:

where u = the initial velocity and v = the final velocity.

Another way in which work can be done is from lifting an object off the ground.  The work done is turned into gravitational potential energy.  Recall that F=mg for falling objects and displacement can also mean height.  Therefore:

 The implication is that the gravitational potential energy will be converted to kinetic energy is a lifted object is allowed to fall.  This will be the subject of the next post.