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Newton’s Laws of Motion Lecture 6 Does this have anything to do with cookies?  Nope, not fig newtons…Sir Isaac Newton  A little bit stuffy, bad hair,

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Presentation on theme: "Newton’s Laws of Motion Lecture 6 Does this have anything to do with cookies?  Nope, not fig newtons…Sir Isaac Newton  A little bit stuffy, bad hair,"— Presentation transcript:

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2 Newton’s Laws of Motion Lecture 6

3 Does this have anything to do with cookies?  Nope, not fig newtons…Sir Isaac Newton  A little bit stuffy, bad hair, but quite an intelligent guy.  He was a genius mathematician & physician in the 1700’s.  During his work, he came up with the three basic ideas that are applied to the physics of most motion.  The ideas have been tested and proved so many times over the years that are now called Newton's Three Laws of Motion.  Check out BrainPop’s Sir Isaac Newton:BrainPop’s  Nope, not fig newtons…Sir Isaac Newton  A little bit stuffy, bad hair, but quite an intelligent guy.  He was a genius mathematician & physician in the 1700’s.  During his work, he came up with the three basic ideas that are applied to the physics of most motion.  The ideas have been tested and proved so many times over the years that are now called Newton's Three Laws of Motion.  Check out BrainPop’s Sir Isaac Newton:BrainPop’s

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5 29. Newton’s 3 Laws of Motion-a

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7 Newton’s Law #1  What does this mean?  If nothing is happening to you and nothing does happen you will never go anywhere.  If you're going in a specific direction, unless something happens to you, you will always go in that direction.  Forever.  Things don’t move unless a force is applied to them.  What does this mean?  If nothing is happening to you and nothing does happen you will never go anywhere.  If you're going in a specific direction, unless something happens to you, you will always go in that direction.  Forever.  Things don’t move unless a force is applied to them.

8 Examples  A golf ball on a tee will remain on the tee until the club, the unbalanced force, makes contact with it.

9 Examples  Think again of astronauts in space.  Have you ever noticed that their tools float?  They can just place them in space and they stay in one place.  There are very few forces acting on objects in space.  When you put something in one place, it will only move very slowly when gravity pulls it.  Think again of astronauts in space.  Have you ever noticed that their tools float?  They can just place them in space and they stay in one place.  There are very few forces acting on objects in space.  When you put something in one place, it will only move very slowly when gravity pulls it.

10 Examples  Objects like to keep doing what they ’ re doing!!!

11 Why don’t things keep on moving forever?  So, if an object in motion remains in motion unless acted upon by another force and I pushed my desk across the room, would it keep moving forever?  Of course not.  It stops moving because an unbalanced force acts on it.  This unbalanced force is friction.  This force is everywhere & affects our daily life constantly.  So, if an object in motion remains in motion unless acted upon by another force and I pushed my desk across the room, would it keep moving forever?  Of course not.  It stops moving because an unbalanced force acts on it.  This unbalanced force is friction.  This force is everywhere & affects our daily life constantly.

12 Example  A tractor trailer will often jackknife on an icy road when the driver suddenly applies the breaks.  The breaks stop the wheels and the front of the rig stops.  However, the back half skids and keeps moving in the direction it was going in.  A tractor trailer will often jackknife on an icy road when the driver suddenly applies the breaks.  The breaks stop the wheels and the front of the rig stops.  However, the back half skids and keeps moving in the direction it was going in.

13 Law #1 = Law of Inertia  Newton’s first law is also called the “law of inertia”  Inertia is the property of an object to resist change in motion.  It is because of inertia that objects like to remain at rest or why objects like to keep moving.  Newton’s first law is also called the “law of inertia”  Inertia is the property of an object to resist change in motion.  It is because of inertia that objects like to remain at rest or why objects like to keep moving.

14 Law of Inertia  To understand inertia, imagine trying to move a bowling ball and a golf ball.  Which needs more force?  Of course, the bowling ball needs more force to get it moving at the same speed as the golf ball.  The bowling ball also needs more force to stop.  A bowling ball has more inertia than a golf ball.  The greater an object’s inertia, the greater the force needed to change its motion.  To understand inertia, imagine trying to move a bowling ball and a golf ball.  Which needs more force?  Of course, the bowling ball needs more force to get it moving at the same speed as the golf ball.  The bowling ball also needs more force to stop.  A bowling ball has more inertia than a golf ball.  The greater an object’s inertia, the greater the force needed to change its motion.

15 Inertia & Mass  Inertia comes from mass.  Objects with more mass have more inertia and are more resistant to changes in their motion.  Have you ever observed the behavior of your mom’s coffee in a coffee cup filled to the rim while starting a car from rest or while bringing a car to rest from a state of motion?  Coffee tends to "keep on doing what it is doing.”  Coffee in motion tends to stay in motion.  Inertia comes from mass.  Objects with more mass have more inertia and are more resistant to changes in their motion.  Have you ever observed the behavior of your mom’s coffee in a coffee cup filled to the rim while starting a car from rest or while bringing a car to rest from a state of motion?  Coffee tends to "keep on doing what it is doing.”  Coffee in motion tends to stay in motion.

16 30. Eureka: Inertia & Mass

17  Have you ever played the “ Blob ” game in the car?  Why is it that when the car turns right, your body goes to the left and when the car turns left, you blob to the right?  You blob in the direction of the car ’ s original motion.  Your body wants to keep going straight, even as the car is turning.  Have you ever played the “ Blob ” game in the car?  Why is it that when the car turns right, your body goes to the left and when the car turns left, you blob to the right?  You blob in the direction of the car ’ s original motion.  Your body wants to keep going straight, even as the car is turning. Example

18  Imagine a dog sitting in the passenger seat of a car.  Suddenly, the brakes are slammed to avoid the bozo driving in front.  What happens to the sweet dog?  She goes flying into the dashboard!  Poor puppy experienced inertia!  Even though the car was stopped by the force of the brakes/friction, she kept going.  A dog in motion remains in motion!  Imagine a dog sitting in the passenger seat of a car.  Suddenly, the brakes are slammed to avoid the bozo driving in front.  What happens to the sweet dog?  She goes flying into the dashboard!  Poor puppy experienced inertia!  Even though the car was stopped by the force of the brakes/friction, she kept going.  A dog in motion remains in motion! Example

19  Or … what happens to your dog when you suddenly slam on the gas pedal? Example

20 Why you must always wear a seatbelt…. ! Look at that inertia!

21 31. Newton’s First Law of Motion

22  blood rushes from your head to your feet while quickly stopping when riding on a descending elevator.  to dislodge ketchup from the bottom of a ketchup bottle, the bottle is often turned upside down, thrust downward at a high speed and then abruptly halted.  blood rushes from your head to your feet while quickly stopping when riding on a descending elevator.  to dislodge ketchup from the bottom of a ketchup bottle, the bottle is often turned upside down, thrust downward at a high speed and then abruptly halted. You should now be able to explain why the following occurs:

23  headrests are placed in cars to prevent whiplash injuries during rear-end collisions.  while riding a skateboard, you fly forward off the board when hitting a curb, a rock or another object which abruptly halts the motion of the skateboard.  headrests are placed in cars to prevent whiplash injuries during rear-end collisions.  while riding a skateboard, you fly forward off the board when hitting a curb, a rock or another object which abruptly halts the motion of the skateboard.

24 32. Newton’s First Law & Roller Coasters

25 Newton’s Third Law  We’re going to skip ahead to Newton’s 3rd law.  We’ll come back to Law #2 tomorrow.  Newton’s first law only applies to single objects.  This third law deals with pairs of objects.  This is because all forces come in pairs.  We’re going to skip ahead to Newton’s 3rd law.  We’ll come back to Law #2 tomorrow.  Newton’s first law only applies to single objects.  This third law deals with pairs of objects.  This is because all forces come in pairs.

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27 33. Newton’s 3rd law

28 Newton versus the Elephant  Imagine a skateboard contest between Newton & an elephant.  They can only push against each other, not against the ground.  The fastest one wins.  The elephant knows it is much stronger & pushes off Newton with a huge force, thinking he will win.  But will he?

29 Newton versus the Elephant  The result of the giant push from the elephant is that Newton flies away with a greater speed & the puzzled elephant moves backwards with a smaller speed.  Newton wins - and will always win, no matter how hard the elephant pushes.  In fact, Newton doesn’t have to push at all & he still wins.  Why?

30 Newton versus the Elephant  Newton wins because forces always come in pairs.  The elephant pushes against Newton & that action pushes Newton away.  The elephant's force against Newton creates a reaction force against the elephant.  These forces are EQUAL in strength.  BUT, these two are different in mass - Newton has a lot less mass & inertia, so he moves more easily.

31 Newton’s Third law  We ’ ve talked about this before.  When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.  There are two forces resulting from this interaction — a force on the chair and a force on your body.  It ’ s a pair of forces!  Action and reaction!  We ’ ve talked about this before.  When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body.  There are two forces resulting from this interaction — a force on the chair and a force on your body.  It ’ s a pair of forces!  Action and reaction!

32 Newton’s Third law  This is how sports work.  How do you hit a baseball?  A golf ball? A tennis ball?  How do you shoot a basketball?  How do you spike a volleyball?  All sports is related to forces & action/reaction pairs.  This is how sports work.  How do you hit a baseball?  A golf ball? A tennis ball?  How do you shoot a basketball?  How do you spike a volleyball?  All sports is related to forces & action/reaction pairs.

33 Examples  Think of how birds fly.  The wings of a bird push air downwards.  In turn, the air reacts by pushing the bird upwards.  For every action, there is an equal (in size) and opposite (in direction) reaction.  Action-reaction force pairs make it possible for birds to fly.  Think of how birds fly.  The wings of a bird push air downwards.  In turn, the air reacts by pushing the bird upwards.  For every action, there is an equal (in size) and opposite (in direction) reaction.  Action-reaction force pairs make it possible for birds to fly.

34 Example  When you swim…your hands and feet push on the water - this is the action force.  The reaction force is the water pushing equally (and in an opposite direction) on your hands and feet.  The reaction forces causes forward motion.  When you swim…your hands and feet push on the water - this is the action force.  The reaction force is the water pushing equally (and in an opposite direction) on your hands and feet.  The reaction forces causes forward motion.

35 Why don’t the forces cancel?  The reason is action & reaction forces act on different objects.  If the two forces canceled each other out, there would be no motion.  Think about throwing a ball.  You apply the action to the ball, creating the ball’s acceleration.  The reaction is the ball pushing back on your hand.  You can only cancel forces acting on the same object.  The reason is action & reaction forces act on different objects.  If the two forces canceled each other out, there would be no motion.  Think about throwing a ball.  You apply the action to the ball, creating the ball’s acceleration.  The reaction is the ball pushing back on your hand.  You can only cancel forces acting on the same object.

36 More examples…

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38 BrainPop: Laws of Motion  Click here Click here  Log on: mms308 password: marshall  Click here Click here  Log on: mms308 password: marshall

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