LESSON: Net Force
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The picture above may look like just another game of tug-of-war but when we look at this picture through the lens of physics we discover that there is a tremendous amount of physics involved. We will use this example of tug-of-war in this section to help us understand the physics concept of net force. |
Net Force
A force is a push or a pull. Net force is the combination of forces that are acting on an object. In other words, net force is a combination of all the pushes and pulls that are acting on an object. In more scientific terms, we would define net force as the resultant vector or the vector sum.
When dealing with net force it is important to remember that forces are vectors. This means that we need to keep track of both the magnitude and the direction. There are two main methods that can be used to keep track of the direction of the force. The first method is to use vector arrows. When using vector arrows the direction the arrow is pointing is the direction of the force. The image below illustrates this concept. You can see that the first force has a magnitude of 40 N and the direction is to the right. The second force has a magnitude of 20 N and the direction is to the left.
The second method used to indicate the direction of the force is to use positive and negative signs (+, -) in front of the magnitude (size or value) of the force. In the example below we see the same forces as in the previous example but now the direction of the forces are indicated using the positive and negative signs.
Calculating Net Force
When forces are operating parallel to each other, we say that they are operating along a straight line. We can find the net force for parallel forces by adding up all of the values. In equation form it would look like this: Net Force = (Force 1) + (Force 2). In the example below we see that the magnitude of each force is 20 N. However the directions of the forces are opposite. The equation for this calculation will look like this: Net Force = (-20 N) + (20 N). When we do the math we find that the net force is equal to zero.
When forces are operating at an angle that is not parallel we need to use vector math. Below are several videos that will teach you graphical methods for solving vector math.
Geometric Vector Operations
Adding Vectors Graphically
Subtracting Vectors Graphically
Scalar Multiplication of Vectors Graphically
Finish this lesson by watching this video of review and examples:
After you have completed this part of the lesson, you can check the associated box on the main course page to mark it as complete 