It is very rare, especially on Earth, to have an object that is experiencing force from only one direction. A bicycle rider has the force of air friction pushing against him. He has to fight against the friction between the gears and the wheels. He has gravity pulling down on him. His muscles are pushing and pulling inside him and so on and so on.


Even as you sit there, you have at least two forces pushing and pulling on you. The force of gravity is pulling you to the center of the Earth. The chair is pushing up on you so you don’t go to the center of the Earth. So with all these forces pushing and pulling, how do you keep track of them all? That’s where net force comes in.


The net force is when you add up all of the forces on something and see what direction the overall force pushes in. The word “net”, in this case, is like net worth or net income. It’s a mathematical concept of what is left after everything that applies is added and subtracted. The next activity will make this clearer.


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Comments

5 Responses to “Introducing the Idea of Net Forces”

  1. Yes, thank you!

  2. Yes, gravitation, resultant “normal” force (counteracting the gravitational force), when I pull the rope one way with the left hand and the other way with the right hand, etc. When you add them all up (using vector algebra), if the sum isn’t zero, it means the rope is moving. If the rope is still, like a bridge is standing still, then the forces are in balance and there is no NET force. Does that help?

  3. What I mean is that are there any examples of forces acting upon the rope in the experiment, specifically, what forces there are and how they are affecting the rope.

  4. Tell me more about your question? I am not sure I am understanding what you are asking.

    The rope experiences the pull from both ends, and also it has weight but for our experiment we’re ignoring the gravitational force.

  5. Are there any other examples of forces that could act upon the rope in the experiment?