Newton's third law pairs
Every force has an equal and opposite force on the other object.
The common mistake
Saying the pair cancels out — they act on different objects, so they can't cancel.
Instead: A third-law pair: same size, opposite direction, same type, acting on two different objects.
Worked example with Guide me
You push a wall with 40 N. What does the wall do?
- Sugar · Which object does the wall push on?Student · Me.
- Sugar · How hard and which way?Student · 40 N, back toward me.
Answer: The wall pushes you with 40 N in the opposite direction.
Try 3 practice questions
1. Earth pulls you down with 600 N. What's the pair?
Show answer
You pull Earth up with 600 N
2. Why doesn't a rocket's pair cancel?
Show answer
The forces act on different objects (rocket and gas)
3. Is weight and the floor's push a third-law pair?
Show answer
No — both act on you
Quick answers
- What is the most common mistake with newton's third law pairs?
- Saying the pair cancels out — they act on different objects, so they can't cancel.
- How do I get newton's third law pairs right?
- A third-law pair: same size, opposite direction, same type, acting on two different objects.
- Can you show a worked example?
- You push a wall with 40 N. What does the wall do? The wall pushes you with 40 N in the opposite direction.
Related concepts
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Save this as a miss — practice it before your test