Physics 2a - Work Done

What is 'Work Done'?

The 'work done' is the same thing as 'energy transferred'. 

To do work, you must move something over a distance.. and to do this, you must have an object to move, a distance to move it over, and a force to move the object - this is the basis of doing work.

For example, work is done when you sweep with a broom: You have to provide a force; an effort to move the dirt over a distance. Energy is being transferred.

(Bear in mind that 'work done' is not always useful - it can be wasted.. especially as heat.)

Formula Triangle!

This is just a simple formula triangle. To find the 'work done', you must times the force by the distance. It is important to remember the units for the triangle. Examiners my try to trick you out by using cm or km instead of meters. Always remember to convert your units!

Let's go straight into an example...

Eg 1: A man pushes a car over a distance of 3m. The man pushes the car with a force of 500N. Find the amount of work done.

 

Work Done = Force x Distance

Work Done = 500 x 3

500 x 3 = 1500J

It's very easy! But let's now look at a more complicated example..

Eg 2: A professional weight-lifter pulls a heavy weight over 500cm with a force of 600N. Find the amount of energy transferred.

Key Notes:

• The unit described here for distance is 500cm. You must convert this into meters.
• Remember.. the "energy transferred" is the same as the "work done", so this question is still asking for the work done even though the wording might be a little different.

Work Done = Force x Distance

Work Done = 600 x 5

600 x 5 = 3000J