Consider what happens when all of the forces acting on an object are in a straight line.
If all the forces are acting in the same direction they are added together. They are pushing in the same direction.
Think of it like you have change in your pocket to buy an item that is 55 cents. You can add up two quarters and one nickel to get to the total of 55 cents. For forces if you need a total of 15 Newtons to move a chair across the floor; you can push with a force of 5 Newtons and your sister can push with a force of 10 Newtons. Together you have the 15 Newtons needed to move the chair.
| 10 N | + | 5 N | = | 15 N |
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In the diagram above the arrows are referred to as vectors, this is a vector diagram. The first two arrows are the force vectors. The third arrow (after the equal sign) is called the resultant vector or resultant force.
When all the forces are in a line this is a simple addition or subtraction problem.
If the forces are acting in opposite directions in a straight line we will simply subtract.
In a tug of war game your team is pulling with a total of 22 Newtons of force and the opposing team is pulling with a total of 10 Newtons. I will draw the force vectors and the resulting vector below for you.
| 22 N | − | 10 N | = | 12 N |
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Try one
What would the force vectors and the resulting force be for the following problem?
Sarah is pushing with a force of 7 N on the car and Ben is pushing in the same direction with a force of 5 N.
