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Newton’s Laws of Motion

Newton’s Laws of Motion. Isaac Newton (1642-1727). Father died before he was born Mother remarried & left him with his grandmother Went to Cambridge – earned his keep by working for other students. Black Death – Great Plague. University closed down Newton returned home

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Newton’s Laws of Motion

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  1. Newton’s Laws of Motion

  2. Isaac Newton (1642-1727) • Father died before he was born • Mother remarried & left him with his grandmother • Went to Cambridge – earned his keep by working for other students

  3. Black Death – Great Plague • University closed down • Newton returned home • Began revolutionary advances in optics, mathematics, physics & astronomy

  4. Academic Life • Became Lucasian Professor at Cambridge • First worked on optics • Equated falling apple with “fall” of moon towards Earth • Explained science of moving bodies

  5. Sir Isaac Newton • 1686 published book- Principia • Three laws that relate force to motion

  6. Newton's First Law • An object at rest remains at rest unless acted on by an unbalanced force • -object will not start to move until a push or pull is exerted on it • Ex- golf ball on tee

  7. Newton's First Law of Motion (Part 2) • An object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force • Ex-rocket ship in space- forever!

  8. Newton's First Law of Motion (Friction) • Objects on Earth slow down & stop moving due to friction • Ex- ball stops rolling on grass • Ex- skateboard stops rolling on pavement

  9. Sum up first law • Matter resists any change in motion • Tendency to resist change called inertia • Mass is a measure of inertia • Ex- Baseball= small mass -easy to start and change motion • Ex- Dumpster= large mass - hard to start and change motion

  10. Another 1st Law Example

  11. Newton's Second Law of Motion • Part 1-Acceleration Depends on Mass • Acceleration decreases as mass increases • Acceleration increases as mass decreases • Ex- empty versus full shopping cart

  12. Newton's Second Law of Motion • Part 2: Acceleration Depends on Force • Acceleration increases as force increases Ex- large force=fastball pitch Ex-small force= tapping golf ball into hole Acceleration always in direction of force To change direction, exert force in direction you want to go.

  13. Second law expressed mathematically • Relationship of acceleration (a) to mass (m) and force (F) • Units- • a = m/s/s • m= kg • F=kg m/s/s (N)

  14. Equation can be Rearranged • a = F/m • or • F= m X a • or • m=F/a

  15. Newton’s 2nd Law & Falling Objects • Compare apple & watermelon • Larger weight offset by greater inertia • Accelerations due to gravity are same for both

  16. Newton’s Third Law of Motion • Forces act in pairs • Action force exerted by one object = reaction force exerted by 2nd object, but in opposite direction

  17. 3rd Law – Think pairs! • Rocket & gases • Push of gas downwards = push of rocket upwards

  18. 3rd Law – Think pairs! • Swimmer & water • Force of swimmer pushing on water = force of water pushing back

  19. Momentum • Property of moving objects • Depends on object’s mass & velocity

  20. P = m X v

  21. Greater momentum requires more force to stop or change object’s direction

  22. Large Truck vs Small Car

  23. Speeding vs Slow Car

  24. Momentum is Conserved

  25. When objects interact, they may exchange momentum, but total amount of momentum stays the same

  26. Bowling Balls & Pins

  27. Wrong & Right Effects

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