Newtons 3rd law of motion isn't always easy to show in a lab. I like this activity for its simplicity and relevance. In this activity, students use BBs and pullback cars to demonstrate how when the car goes forward, it's pushing backward on the ground. Extension ideas are provided for digging deeper to help solidify the concept for students. Most students have the sense that only people can exert a force such as a push--and don't realize that walls, tables, the ground, etc can push things too. This surprising fact is fundamental to understanding Newton's third law.
- For every action there is an equal and opposite reaction.
- The forces are opposite in direction and equal in degree, (the accelerations--change in movements depend on the size of the object being moved).
- Forces always come in pairs.
Materials Needed per setup: pull-back car, BBs or pellets, cardboard, large box or tray
Prep Needed Gather supplies
Teaching Time 20-30 min
Related Labs Motion and Newton's Laws
Force and Motion: Action Reaction Demo in the Lab and Real Life
Answer Keys and Teacher Notes address most questions and issues that might arise in this study—you shouldn’t have to do any outside research unless you want to.
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