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Warm-up 2/16/11. Review: Tell me anything you can think of about Newton’s Laws (even if it’s the obvious). Review: List any forces acting on you now as you sit in your desk and if you were to get up and give me a dollar. - PowerPoint PPT Presentation
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Warm-up 2/16/11
Review: Tell me anything you can think of about Newton’s Laws (even if it’s the obvious).
Review: List any forces acting on you now as you sit in your desk and if you were to get up and give me a dollar.
Teach the Teacher: Who is the most inspiring person in your life (besides me)?
Newton’s Laws of Motion They are hard to break
NEWTON If I have seen farther
than other men, it is because I have stood on the shoulders of giants." -Isaac Newton
When Newton made that famous statement, he was referring to such giants as Tycho Brahe, Johannes Kepler, and, most specifically, Galileo Galilei
History behind the First Law of Motion
Prior to Galileo and Newton's work on motion, it was believed that the natural tendency of objects was to come to rest. › Sooner or later, moving objects would stop moving. › Meaning that some force was necessary to keep an
object in motion. Aristotle and Ptolemy.
Galileo boldly asserted the exact opposite. He reasoned that moving objects eventually
stopped moving due to a force called friction. Galileo's Experiment Galileo developed the concept of inertia.
The ball would roll forever…..Like in space
Newton’s First Law of Motion - INERTIA Objects at rest stay at rest unless acted on by another force. Objects in motion stay in motion unless acted on by another force
There is a natural tendency for objects to resist changes in their state of motion.
Inertia
INERTIA – The resistance of an object to a change in its state of motion.
The more mass an object has, the greater inertia.
Shooting Objects at RestThe object’s inertia causes it to remain still
even when a bullet passes through it.
FORCE
› is a push or a pull › can give energy to
an object causing the object to: start moving, stop moving, change its motion.
Force, Mass & Acceleration
For any object, the greater the force applied to it, the greater its acceleration.
The acceleration of an object depends on its mass as well.
Force, mass, and acceleration are connected.
Balanced vs. Unbalanced Balanced forces
› They are equal in size and opposite in direction
› Do NOT cause a change in motion.
› Result in a zero net force Net force is the
result of all the forces acting on the object
Unbalanced forces › They are
unequal in size and or in the same direction
› Cause a change in motion
Units
The SI unit for mass =kilogram (kg)
The unit for acceleration = meters per second squared (m/s2)
So the unit for force = kg x m/s2
The kg x m/s2 is called the newton (N)
Tugboat Problems Two tugboats are moving a barge. Tugboat
A exerts a force of 3000 Newtons on the barge. Tugboat B exerts a force of 5000 Newtons in the same direction. What is the combined force on the barge? Draw arrows showing the individual and combined forces of the tugboats.
Tug Boat Questions
Now suppose that Tugboat C exerts a force of 2000 Newtons on the barge and Tugboat D exerts a force of 4000 Newtons in the opposite direction. What is the combined force on the barge? Draw arrows showing the individual and combined forces of the tugboats.
Tugboat questions
Could there ever be a case when Tugboat E and Tugboat F are both exerting a force on the barge but the barge doesn't move? Draw arrows showing the individual and combined forces in such a situation.
Physics To Win It Challenge
http://www.nbc.com/minute-to-win-it/how-to/keep-the-change/
The Challenge: pull an index card from under a penny and have it land in the cup 3 times within a minute.
On index card explain how inertia is effecting the card and penny
Warm-up 2/18/11
Review: Give as many examples of a force as you can think of ( ex: pulling a puppy across the room)
Teach the Teacher: What is your favorite salad dressing?
Flash Card
On the front write:
Inertia
On the back write:
The resistance of an object to a change in its state of motion.
Flash Card
On the front write:
Newton’s First Law
On the back write:
Objects at rest stay at rest
Objects in motion stay in motion…. unless acted on by another force
Flash Card
On the Front write:
Force
On the back write:
› is a push or a pull › can give energy to
an object causing motion
Newton’s Second Law The acceleration of an object is
dependent upon the force acting upon the object and the mass of the object.
Actions into Equations
Newton’s Second Law can be written as the equation:
F = m x a F = force (N) Newton is
the SI Unit of force m = mass (kg) N = kg m / s2
a = acceleration (m/s/s)
Solving the 2nd Law
Friction A force that opposes motion
between two surfaces that are touching each other
The amount of friction is dependant upon› Surfaces› Force pressing the surfaces
together
Types of Friction Static Friction
› Friction between two objects that are NOT moving.
Sliding Friction› Friction between two surfaces moving
past each other. Rolling Friction
› Friction between a rolling object & the surface it is rolling on.
Fluid Friction › Friction between an object and a gas or
liquid
Encarta Friction Animation
Who am I?
Acceleration Speed Inertia Force Velocity Friction Gravity Newton
Warm-UP 2/23/11
Review: In your notes put a star by the two of newtons laws that we have covered so far.
Teach the Teacher: What is your
favorite cereal?
Flash Card
On the front write:
Balanced forces
On the back write:
No motion, zero net force,
Flash Card
On the front write:
Unbalanced forces
On the back write:
Motion occurs, either add or subtract to get net force
Flash Card
On the front write:
Newton’s 2nd law
On the back write:
Acceleration of an object depends on the mass and force
F=ma
Who am I?
Velocity Speed Friction Acceleration Unbalanced force Balanced Force Newton’s Second
Law
Force Newton’s First
Law Inertia
Warm-Up 2/25/11
Review: Draw the triangles for speed, acceleration, and force
Teach the Teacher: What is your favorite type of activity in this class (notes, labs, whiteboard challenge,ect) What is your least favorite?
Physics To Win It
Hole in One Challenge: To roll a golf ball off the ramp,
off the table, and land in the cup…I have to see it.
Jackpot challenge: To get a golf ball to do the above, bounce once and land in the cup
On an index card calculate the velocity of the ball
Air Resistance When an object falls, it is pulled
downward by gravity. Air resistance—a force that
acts on objects as they fall through the air.
The amount of resistance on an object depends on the speed, size, and shape of the object.› A feather will fall more slowly than
an apple
Air Resistance Dependent on…
a variety of factors, most importantly› the speed of the object
Increased speeds = increased air resistance.
› the cross-sectional area of the object Increased cross-sectional area =
increased air resistance.
List the examples of friction in this picture
Gravity Universal law of Gravity
› Any two objects will exert an attractive force on each other
› The size of the force is dependant on Mass of both objects Distance between
the objects
Falling Objects on Earth
Near Earth’s surface Acceleration due to
gravity › 9.8 m/s2 or ~ 10 m/s2
If a bowling ball and a marble are dropped from the same height, which would hit the ground first?
Simultaneous drop of two objects with different massesdropping objects on the moon
Weight vs. Mass Weight
› Force of gravity pulling you toward the earth
› SI Base Unit = Newtons› Weight can change with a
change in location. Mass
› A measure of how much matter any object has
› You know an object has mass because it has inertia
› SI Base Unit = Kilograms › http://www.exploratorium.edu
/ronh/weight/
Warm-Up 3/1/11
Review: Draw a picture of an example of friction (use your notes!)
Teach the Teacher: If you could be any animal what would you be?
Learning Target: › Factors that effect air resistance › Difference between weight and
mass
Air Resistance Challenge Put your name on both sheets of paper One sheet=design a “papercraft” that
will have A LOT of air resistance Other sheet=design a “papercraft”
that will have VERY LITTLE air resistance
WHEN DROPPED FROM THE SECOND STORY BALCONY
YOU WILL FAIL IF YOU DON’T PICK IT UP!
Air resistance Challenge Card
On one 3x5 card describe your design for the “papercraft” that had A LOT OF air resistance
And tell me why you think it did. On the other 3x5 card describe your
design for “papercraft” that had VERY LITTLE air resistance
And tell me why you think it did.
Flash Card
On the front write:
Air resistance
On the back write:
A force on objects as they fall through the air.
Flash Card
On the front write:
Gravity
On the back write:
An attractive force between two objects depend on the mass and distance between them
Flash Card
On the front write:
Mass
On the back write:
The amount of matter in an object, doesn’t change
Flash Card
On the front write:
Weight
On the back write:
The force of gravity pulling on you, changes in the universe
Roll Say Flash
Materials: Flash cards, game board, dice, partner
While one person is rolling the dice, another person is flipping over flash cards. And seeing if they can say the word, and putting it in appropriate place on game board
The other person is the judge, until they roll a six then trade
Keep playing until the music stops and the one with the fewest, “got it on the first try” has to move to the next table
Warm-up 3/3/11
Review: What are newton’s laws that we have looked at so far? USE YOUR NOTES!
Teach the Teacher: What is the best
pair of shoes you have ever owned? Learning Target: Types of Friction
American Indian Physics Contributions Related to Friction
Contribution: canoe, pulleys, ect, Friction Force Used: sliding or rolling
or static ect. Region or Tribe to Thank: Other interesting fact: ADD PICTURE AND SOURCE OF
PICTURE!
Warm-up 3.7.11
Review: List as many flash card words as you can think of.
Teach the Teacher: What is your top 3 restaurants in Rapid?
Target: Newton’s Third Law
NEWTON’S 3rd LAW
For every action, there is an equal and opposite reaction
“Action” and “Reaction” are names of forces
Forces ALWAYS occur in pairs Single forces NEVER happen action reaction pairs
“Equal” In Newton’s Third Law, “equal”
means:
Equal in size.› The action and reaction forces are
EXACTLY the same size.
Equal in time.› The action and reaction forces
occur at EXACTLY the same time.
& Opposite
In Newton’s Third Law, “opposite” means:
Opposite in direction› The action and reaction forces are
EXACTLY 180o apart in direction.
Why don’t the forces cancel each other out?
Only forces pushing or pulling on an object affect the object’s motion.
Only forces that act on the same object can cancel.
Newton’s Third Law action and reaction forces act on different objects, so they don’t cancel.
Writing Action Reaction Forces
Action force: “A action verb B”
Reaction force: “B action verb A”
› ACTION
Bowling ball hits the pin to the left.
› REACTION
Pin hits the bowling ball to the right
The action and reaction forces don’t cancel since they push on different objects.
Momentum
A property related to how much force is required to change the objects motion
The product of the objects mass and velocity
p = mv› p = momentum› m = mass› v = velocity
SI UNIT = Kg m / s
Law of Conservation of Momentum
Momentum may be transferred to another object
The total momentum before a collision is equal to the total momentum after the collision
m1v1 = m2v2 interactive
Physics To Win it Challenge
Back Flip
Front of 3x5 card: draw a diagram of the forces working on your hand and pencil before the flip
Back of 3x5 card: draw a diagram of a the forces working on your hand and pencil during the flip
Warm-up 3/14/11
Review: Draw as many equation triangles as you can remember.
Teach the Teacher: What was the high point of your weekend?
What was the low point?
American Indian Physics Contributions Related to Friction
Contribution: canoe, pulleys, ect, Friction Force Used: sliding or rolling
or static ect. Region or Tribe to Thank: Other interesting fact: ADD PICTURE AND SOURCE OF
PICTURE!
Warm-Up 3/16/11
Review: What is the hardest part of Newton’s Laws, What is the easiest?
Teach the Teacher: Tell me a favorite memory of you as a kid, what was something that stands out to you.
Learning Targets: all of newton’s laws
Warm
