Eighth Grade · Science · week 5

Action-reaction pairs

State Newton's third law and identify the action-reaction force pair in real situations.

Newton's third law says every action force has a reaction force equal in size and opposite in direction. You cannot push on something without it pushing back on you just as hard.

The trick is naming both forces correctly: they act on two different objects, at the same time, equal in strength, opposite in direction. Pushing off a wall while swimming: your hand pushes the wall backward (action), and the wall pushes your hand forward (reaction) -- that reaction sends you gliding.

📋 For the teacher
Teach it (10–15 min):
  • Have them push gently against a wall and describe what pushes back -- the reaction force is a real sensation, not an abstraction.
  • Practice naming both halves of every pair, including which object each force acts on.
  • Clear up the "they cancel out" mix-up directly: the two forces act on different objects.
Talk about it:
  • Why do action-reaction forces not cancel each other out?
  • How does a swimmer use Newton's third law to move through water?

Mastery looks like: They correctly identify both forces in an action-reaction pair, naming which object each force acts on.

Common stumbles: Thinking the two forces act on the same object and cancel out; naming only one half of the pair.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Science for this learner.
← Back to todayAll coursesYear planner