Forces are measured in newtons (N). The main force is gravity, which affects every object on Earth.

## Resultant forces

The resultant force of an object is worked out by subtracting the strongest force with the weakest force. The result is the direction of the strongest force with the result of the subtraction being the “resultant force”. Below is an example:

## Work done

The “work done” is the amount of energy “spent” moving an object. The formula for working this out is below:

work done (joules) = force (newtons) x distance (metres)

### Example questions

If Bob moved a box with a weight of 25N by 5m, what would be the work done?

The answer to that question would be 125J because 5 x 25 = 125.

Catherine used 100J on moving a box by 2m. How much force was used?

In order to answer this question, you need to rearrange the formula so you are working out the force rather than the work done. So work done = force x distance becomes force = work done ÷ distance.

That means the answer to this question is 50N because 100 ÷ 2 = 50.

## Rearranging formulas

There are 3 steps to rearranging formulas: putting the formula into a triangle, covering up the value you want to find out and using the triangle to make a new formula.