Newton's Third Law: Action-Reaction Forces

Grade 8 Physical Science Understanding Forces and Motion Next Generation Science Standards (NGSS)

What is Newton's Third Law?

For every action, there is an equal and opposite reaction Forces always come in pairs Action and reaction forces act on different objects The forces are equal in size but opposite in direction

Demonstration Time!

Watch the spring-loaded cart demonstration Observe what happens to both carts Think about the forces involved Record your observations

Identifying Action-Reaction Pairs

{"left":"Person walks forward\nEarth pushes back on person's feet\nRocket engines push gas downward","right":"Gas pushes rocket upward\nSwimmer pushes water backward\nWater pushes swimmer forward"}

Think-Pair-Share

Why don't action-reaction forces cancel each other out? Discuss with your partner for 2 minutes Be ready to share your ideas with the class

Drawing Force Diagrams

Use arrows to represent forces Label the action and reaction forces Show the direction with arrow direction Make arrow length represent force strength

Real-World Applications

Your Turn: Design Challenge

Design a balloon-powered vehicle Apply Newton's Third Law principles Sketch your design and label forces Test your vehicle if time permits