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Name: _______________________________ Class: ____ 12.3 Newton’s 3rd Law of Motion

Name: _______________________________ Class: ____ 12.3 Newton’s 3rd Law of Motion. Chapter 12 Forces and Motion. What are we going to learn?. Newton’s 3 rd Law of Motion. Newton’s 3 rd Law of Motion.

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Name: _______________________________ Class: ____ 12.3 Newton’s 3rd Law of Motion

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  1. Name: _______________________________ Class: ____ 12.3 Newton’s 3rd Law of Motion Chapter 12 Forces and Motion

  2. What are we going to learn? • Newton’s 3rd Law of Motion

  3. Newton’s 3rd Law of Motion • If one __________ exerts a __________ on another object, then the _______________________ exerts a __________ of __________ strength in the ________________________ on the first object (for every ___________ there is an __________ but _________________________________) • Ex: If you ____________ against a ________ and it didn’t _________________ on you, you’d _____________________________. What does that mean? • Equal and opposite means _____________________ ____________________________________________

  4. Action-Reaction Pairs • __________ of ___________ and __________________________ are all around you. • Ex: When you _________, you push ______________ on the _____________ with your feet (_____________________) and the ground _____________ forward on your _________ with an equal and opposite force (_____________________). • Ex: A _______________ moves _____________ by exerting an ___________ force on the __________ with her hands. The __________ pushes on her hands with an equal ________________ force that ___________ her ___________________________.

  5. What force is not labeled? ______________________ • Is there a force that cancels out gravity? ___________ • What would happen to the volleyball if the players take their hands away from it? _____________________________________________

  6. How does the diagram illustrate Newton’sthird law of motion? __________________________ __________________________ __________________________ Examples • Suppose you hit a nail with a hammer, exerting a force on the nail. What is the reaction force? ____________________________________________ ____________________________________________ • What are the action and reaction forces involved in jumping on a trampoline? ____________________________________________ ____________________________________________

  7. A volunteer please... • Why is it easier to move the chair by pushing off the floor? _____________________________________________ _____________________________________________ _____________________________________________ _____________________________________________ Another volunteer please... • What happened when the volunteer tossed the ball? _____________________________________________ • What made the volunteer move? _____________________________________________

  8. Detecting Motion • If you ________ your _______, gravity _________ the pen ____________________. • According to Newton’s ______ law, the ___________ Earth ________________ with an _________ and _______________ reaction _________. • You see the ______________, but you _________ see ____________ accelerate _________ the _____. • Why??? • According to Newton’s _____ law, if ____________________ and __________ stays the ________, _________________________________. • The same ______________ on both ________ and your ______ but ________ has such a ____________ that its _______________ is so _______ you don’t notice it.

  9. Do Action-Reaction Forces Cancel? • If ____________________ acting in _____________ _______________ on an object ________ each other out and produce _____________________________, why don’t the action-reaction forces of Newton’s third law of motion cancel as well? • ___________ and _____________ forces ____________________ out because they ___________________________________________ • Ex: _____________ exerts action on _________, but water exerts a ____________ force on the swimmer’s _________

  10. I get it! Now I know that Newton’s third law states that ___________________________________________

  11. In jet engines, the exhaust _________ are pushed ______ of the ____________, and the gases push _____________ the _________, pushing the ______________________(think of an air-filled balloon that is opened to release the air) What makes the Bug go Splat? • What happened to the driver when she braked suddenly? _______________________________________ • Why didn’t she hit the windshield when she braked? _____________________________________________

  12. What forces act when a seatbelt stops a driver from moving too far forward? _____________________________________________ _____________________________________________ _____________________________________________ • What must happen for the bug to stop moving at constant velocity? _____________________________________________ • What must happen for the bug to stop moving at constant velocity? _____________________________________________ • How will this difference affect the collision? _____________________________________________ _____________________________________________

  13. Buzz! • In order for the bug to fly through the air, a force has to push the bug forward. Identify this force. How does the bug produce it? (Hint: think back to how a swimmer moves through the water.) _____________________________________________ _____________________________________________ _____________________________________________ _____________________________________________ • The bug was at rest on a tree when it saw the car and decided to fly toward it. If the bug has a mass of 0.05 kg and accelerates at 2 m/s2, what’s the net force on the bug? _____________________________________________

  14. Vroom! • The driver hates killing bugs. When she saw one coming toward the windshield, she braked suddenly and hoped it would get out of the way. (Sadly, it did not.) When she hit the brakes, she felt that she was thrown forward. Use one of Newton’s laws to explain why. _____________________________________________ _____________________________________________ _____________________________________________ Splat! • The unfortunate bug hits the windshield with a force of 1 N. If you call this the action force, what is the reaction force? _____________________________________________

  15. Does the car hit the bug any harder than the bug hits the car? Use one of Newton’s laws to explain why or why not. _____________________________________________ _____________________________________________ _____________________________________________ • Compare the forces on the bug and the car again. Use another one of Newton’s laws to explain why the bug goes splat and the car keeps going, without noticeably slowing down. _____________________________________________ _____________________________________________ _____________________________________________

  16. Questions • True or false. If the statement is false, change the underlined word(s) to make the statement true. • _______ If you increase the force on an object, its acceleration increases. • _______ If you increase the mass of an object, its acceleration decreases. • ______ To accelerate a 3 kg skateboard at 9 m/s2, a force of 3 newtons is needed. • ______ The amount of inertia an object has depends on its speed. 5. ______ Newton’s first law of motion states that an object will not experience a change in motion unless acted upon by a(n) balanced force.

  17. 6. ________ To increase acceleration of an object, you reduce its mass or increase the applied force. 7. ________ Newton’s third law of motion states that if one object exerts a force on another object, then the second object exerts a force of equal strength in the same direction. 8. ________ Resistance to change in motion is called stasis. 9. ________ Action and reaction forces acting in opposite directions do cancel out because they act on different objects. 10. _______ If you lean against a wall, the wall pushes back on you with a(n) weaker force. 11. _______ Newton’s second law of motion states that an object’s acceleration depends on its distance and on the net force acting on it.

  18. 12. _______Acceleration is measured in m/s2. 13. _______ Force is measured in a unit called the N. 14. _______ The smaller the mass of an object, the more its inertia.

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