Work in physics is generally referred to as a change in energy.  In physics 11 we look at two different energy changes in particular.  Gravitational potential (the energy of height) and kinetic (the energy of motion). 

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Let’s look first at calculating work when changing the height of an object.  Remember that work in this case is calculated as the change in energy.  So (Ef – Ei)  Try watching this video and then trying some on your own below.

 

Next we will look at calculating work when changing the velocity of an object.  Remember again that work in this case is calculated as the change in energy.  So (Ef – Ei)  Only this time instead of calculating the gravitational energy before and after, you will calculate the kinetic energy.  Also remember that if you are slowing an object down that it will count as Negative Work.  Try watching this video and then trying some on your own below.

 

In both of the above examples we looked at solving work as a change in energy.  In the below examples we are going to look at work as a separate equation which is W = Fd, work is equal to force applied multiplied by the distance over which it is applied.  The practice questions do two different genres.  One where we know the force that is being applied, and a second where we need to calculate the force of friction and then realize that the force applied must be equal to friction.  This happens anytime an object is being pushed at a constant velocity.

 

Finally in our last example we are going to look at situations in which work is being done by friction and therefore energy is being lost by our system.  In these situations we calculate the energy at the end and the energy in the beginning and we realize that the difference in energy is the work done by friction.  The example that we use is a child going down a slide.  And yes, the example is one of those hot metal slides from the 80s that would always get super hot in the sunshine and built character!  If you didn’t lose energy due to friction, the child would quite literally fly off the bottom of the slide.  It would be the same as falling.  Check out this example problem below and then try to see if you can solve some.