UNITS OF WORK

How do you determine if work
has been done? In science,
specific conditions have to be
met to determine work done.


OBJECTIVES FOR THIS LESSON:
At the end of this lesson, there will be a short quiz that will ask you
questions about these objectives and you should be able to write a
response to each of the statements below:

Work
is a quantity that
measures a force acting
on an object over a
distance.

So in the everyday world, if we say that we are going to work, we
may not being doing work in the scientific definition. In order to
determine if work is being done, you need to think about the object
on which a force is being applied.


Let's think about a weight lifter. If a weight lifter is holding a barbell
steady over his head, he is not doing any work. The barbell is the
object on which he is applying a force, but he is not moving the
barbell over a distance. He is holding it still over his head, so since
the weight is not moving, there is no work done.
The lifter did do work as he lifted the barbell from the floor and over his head. 
"I did more work than you!"
"No way, I did more!"

Can the amount of work done be measured? Sure! As with any
physics concept, there is an equation that lets us put in known
measurements to determine an unknown value. Let's look at
measuring work.

Work is calculated as force times distance.
W = Fd


Look at each of the pictures.
Force is being applied to
objects to move them a
distance.
The forklift will apply a force to
move the stack of wood across
the lumber yard.
The shopper will apply a force to move the cart and the groceries down the grocery isle. 
Work is measured in units of newtons times meters.
You should remember that the SI unit for force is newtons
and that a newton is a derived unit (1kg x 1m = 1N).

The unit for work is also a derived unit. Work is measured in
joules (J). A joule is equal to 1kg x m^{2}/s^{2} .

1N x m = 1J = 1kg x m^{2}/s^{2}

Since all of these units are equal, you can use any of the above
units when solving work problems. This will make canceling out
other units in the problem much easier.
It's time to begin solving work problems.
