6.7C TEKS Notes

Newton's Third Law of Motion

Introduction

  • Ability to identify simultaneous force pairs from interactions between objects.

  • Focus on forces' magnitudes and directions as explained by Newton's third law.

Forces and Magnitudes

  • The size of forces is referred to as magnitude.

  • Larger forces (>100 newtons) have larger magnitudes (ex: 200 newtons vs. 100 newtons).

Overview of Newton's Third Law

  • Definition: For every action force, there is an equal and opposite reaction force.

  • Sir Isaac Newton:

    • Born in England in 1643.

    • Known for formulating the three laws of motion.

Simultaneous Force Pairs

  • Forces always act in pairs known as simultaneous force pairs.

  • Characteristics:

    • Exist between two objects involved in an interaction.

    • Are equal in magnitude and opposite in direction.

  • Notable Example: Both Earth and humans exert gravitational forces on each other:

    • Humans pull on Earth, and Earth pulls back, however, due to differing masses, humans experience noticeable effects.

Practical Examples of Newton's Third Law

  • Balloon Example:

    • Inflation due to air molecules pushing against the surface of the balloon.

    • Upon release, the balloon pushes air out, leading to forward motion.

    • The simultaneous force pair: balloon and air molecules.

  • Swimmer Example:

    • The swimmer pushes off the wall, showcasing the action-reaction force pair.

    • Action: Swimmer pushes against the wall.

    • Reaction: Wall pushes back against the swimmer.

    • While the swimmer moves forward, the wall remains stationary due to its larger mass.

  • Boy and Boat Example:

    • The boy applies force to push the boat away from the dock.

    • Simultaneous force pair: boy and boat, illustrating similar dynamics as previous examples.

  • Rocket Example:

    • Rockets push exhaust gases backward, but gases simultaneously push back against the rocket.

    • This interaction propels the rocket upward into space.

Summary of Key Concepts

  • Newton's Third Law of Motion:

    • States that when two objects interact, they exert forces on each other of equal size and opposite direction.

    • A simultaneous force pair is formed between the interacting objects.

  • Understanding of magnitude: refers to the size or intensity of a force.

Conclusion

  • Mastery of identifying simultaneous force pairs that follow the principles outlined in Newton's third law.