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Newton's 3rd Law of Motion: Action/Reaction Law

Author: Michele Langhans

Newton's 3rd Law of Motion

Notes on Newton's 3rd Law of Motion and examples

Source: Langhans

Newton’s 3rd Law: These are the “S” in WSQ. You must have them under your video notes completed by the due date on the Unit Plan.


1.     Newton’s 3rd Law says:

2.    What does Newton’s 3rd Law mean?

3.    Action and Reaction forces come in pairs: fill in the missing force

a.    I push on desk, _____________________

b.    Car pushes on road, __________________

c.    Bird pulls on worm, ___________________

4.    I push east on a wall with a force of 20N.  What is the magnitude and direction of the reaction force?

5.    A mosquito flies along and runs into the windshield of rapidly moving vehicle. Which force is stronger, the force of the windshield hitting the mosquito or the force of the mosquito hitting the windshield? Explain.

6. Identify 6 Action/Reaction pairs in the diagram below:


7.     You are free-floating in outer space at a complete standstill.  Your jet propeller just ran out of gas.  The space shuttle is 20m away and no one else is inside.  For a brief moment you panic and fear all is lost.  Then suddenly you remember the wonderful lessons taught by your brilliant Science teacher.  Although it once seemed strange that you were carrying a bowling ball with you in outer space you are now thankful it is with you.  How can the bowling ball and Newton get you out of this jam?

8.    A farmer has just loaded up her cart with all sorts of vegetables grown her farm.  She hooks the donkey to the cart and says GIDDYAP!  However, the donkey was watching a little Bill Nye and thought he knew Newton’s 3rd law.  He says to the farmer: “It won’t do no good to have me pull on this cart.  If I pull on the cart, it’s just gonna pull me with an equal force in the opposite direction.  We won’t get anywhere.”  What can the farmer tell the donkey to convince it that it can pull the cart along the ground?

Source: Langhans

Newton's Laws: HOT question

1. A question that you are still confused about (be specific, include which part of the video, etc)
2. A question that connects the videos together (i.e. asking about the relationship between the content)
3. A question you think you know the answer to, but you want to challenge your classmates with
Use your Unit Plan to help with question starters

Source: inspired by C. Kirch