MATH - SCIENCE INTEGRATION

bullet1 POWER AND MECHANICAL ADVANTAGE

bullet2 POWER


bullet3 Definition of Power

DEFINITION:  Power is a quantity that measures the rate at which work is done.

Power is measured by dividing the amount of work done by the time it takes to complete the work.  The equation for power is:

power =  work        or     P =  W
               time                         t
  • The SI unit for power is a unit called the watt.  The watt is another derived SI unit.  You should remember that a derived unit is one that is made up of two or more SI units.  

1 watt = 1 joule           
              1 second

1 watt is the amount of power needed to do 1 joule of work in 1 second.  
  • The SI unit for work is joule (J).
  • The SI unit for time is second (s).




bullet3 Objectives


After finishing this lesson on power, you should be able to complete each of the following objectives:
  • Define power.
  • Write the equation for power and identify all of the parts.
  • Know the SI units involved with measuring power.
  • Solve power problems.

After you finish the lesson, you can prepare for your chapter quiz or test by completing the quiz on this site.



bullet3 Why measure Power?

Measuring power allows you to compare two machines and their work output.  If two machines do the same amount of work, but one does it in a shorter period of time, then that machine has more power.

With the equation for power, you can compare two weightlifters.  If both lifters raise barbells at the same time, but one lifts 200N and the other lifts 500N, then the last one has more power.  

A unit of power that you might be familiar with is horsepower (hp).  Horsepower originally measured the average power output of a draft horse.  There is a conversion factor that can be used to compare horsepower to the watt.  
1 horsepower = 746 Watts