Force and Laws of Motion

Have you stood in a bus when the driver braked hard? You moved forward, and nobody pushed you. Why did that happen? In this chapter we find out. We learn what a force is and how a force changes the way things move. We also see why every push has a push back. Newton explained all of this with three laws. We discuss them one at a time, and we use Python to watch them work.

Part of Physics · High School (9–10) (chapter 2)

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Forces and the First Law

You push a door. You pull a rope. Gravity pulls you down. All of these are forces. Here we learn how to add forces together and how to tell if they are balanced. Then we meet Newton's first law, and we see why a moving thing likes to keep moving.

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The Second Law and Momentum

Push a toy car with a force. Push a loaded truck with the same force. They do not speed up in the same way. Why not? This course gives the rule. It is Newton's second law. We also meet momentum, which tells us how hard a moving thing is to stop.

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More onMechanics › Newton's Laws of Motion Mechanics › Momentum and Collisions Mechanics › Friction

The Third Law and Conservation of Momentum

When you push a wall, the wall pushes you back. This is Newton's third law. It explains how a swimmer moves forward and why a gun moves backward when it fires. At the end we see why the total momentum of colliding objects does not change.