Power Problems!  Give me more!

Basic Formula: P = W / t P = (F x d) / t
P = power W = work t = time
  W = F x d (click for the page on calculating work)
Units: Power will usually be expressed in J/sec which is also defined as the unit Watts (W)  A watt is equal to 1 Joule per second.
Work will always be a distance unit times a force unit. It is usually a newton*meter (Nm) - also known as a Joule (J)
Time units: usually in seconds

 

These problems are not really very hard to solve as long as you match the given numbers (usually using their units) with the formula above.  You can also use the triangle method.  The triangle is an easy way to figure out how to manipulate the formula.  In order to use it, look at the triangle.  Put your finger over the variable or letter you need to solve for.  For example, if you are looking for power, you will cover up the letter P.  Now you do the mathematical function it shows.  If the letters are beside each other, you multiply.  If one is on top of the other, you divide.  If you would like to check out some sample problems, click on this link:  <power sample problems>
The triangle:

You can see that if you were trying to solve for Power need to do know how much work was done in what amount of time, so if you covered up the P, then the W(J) would be over the time (sec), so you would divide the work done by the time you took to do it.  Similarly, if you wanted to solve for the amount of time the work took,  then the work(J) would be divided by the Power (Watts) you applied since the work(J) is on the top. If you wanted to solve for the work(J) it took to complete the task, then the Power (Watts) would be located beside the time (sec), so you would multiply them together. 

(Units are included in italics in the parenthesis)

 

Last Updated: April 8, 2005.  All Rights Reserved.  If you have any questions or comments, please contact the IPCWebmaster. test