Transcript Newton`s Three Laws

Newton’s Three Laws
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IQ
12/16/13
page 70
• Why does a bowling ball eventually stop
when you throw it down the lane? Explain
using scientific terms.
Athletes use spinning, pushing and bumping
motions to score points.
• Can you think of some examples?
Newton’s First Law of Motion
• An object at rest remains at rest unless acted
on by an unbalanced force.
• An object in motion continues in motion with
the same speed and direction unless acted
upon by an unbalanced force.
• This law is often called “the law of inertia".
What does inertia mean?
• Objects tend to keep on doing what they're doing.
• Inertia depends on the mass of the object.
• The more massive the object, the more it resists
changes in its motion.
Real World Examples…
• Soccer
If I kick a soccer ball
towards the net and the
goalie is not there to stop
it…
GOAL!!!
• Bowling
When I roll the bowling
ball down the lane, it
will keep going until it
hits the pins… or the
gutter!
How can I describe a “magic
trick” in terms of forces?
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Materials:
Cup
Playing card
Coin
• Create a hypothesis:
1) Suppose you were to flick the card, sending it flying horizontally.
What would happen to the coin? Why?
2) Suppose you were to slowly pull the card horizontally from the
mouth of the cup. What would happen to the coin? Why?
Conclusions:
3) Which forces acted on the coin before the card moved?
4) Which forces acted on the card as it moved?
5) Using Newton’s Laws of Motion, explain what happened to the coin
when the card was flicked.
• Conclusions:
• 3) Which forces acted on the coin before
the card moved?
• 4) Which forces acted on the card as it
moved?
• 5) Using Newton’s Laws of Motion, explain
what happened to the coin when the card
was flicked.
•
How do magicians perform the
tablecloth trick?
IQ
12/17/13
pg 72
• Would it take more force to push a car or a
bike? Why? Explain
Newton’s Second Law of Motion
• Acceleration (change in speed or
direction) is produced when a force
acts on a mass. The greater the mass
(of the object being accelerated) the
greater the amount of force needed (to
accelerate the object).
Which situation would require
most force?
• Heavy shopping cart vs. empty shopping cart
• Stopping a person on a bike vs. catching a
basketball
• Kicking a tennis ball and kicking a bowling ball
• Pushing a 40 kg box vs. pushing a 1 kg box
• More mass-more force to move object
• Less mass-less force to move object
What does the 2nd law mean?
• Heavier objects require more force to
move the same distance as lighter objects.
•
Real World Examples
• If you are a defensive
lineman, who would
be easier to tackle…
A running back that
weighs 100 pounds
or a running back
that weighs 300
pounds?
IQ
12/18/13
pg74
• Which one of Newton’s Laws is the
relationship between amount of force
needed to accelerate an object’s mass?
Newton’s Third Law of Motion
• For every action there is an equal and
opposite re-action.
• If one object exerts a force on another
object, then the second object exerts a
force of equal strength in the opposite
direction on the first object.
• Action and reaction forces in a pair do not
act on the same object, otherwise nothing
would move.
Equal but Opposite
What does this mean?
This means that for every force there is
a reaction force that is equal in size,
but opposite in direction. That is to say
that whenever an object pushes
another object it gets pushed back in
the opposite direction equally hard.
In the Real World…
• Golf
When Tiger Woods hits
the golf ball…what is the
reaction?
• Racing
• When Dale Earnhardt
steps on the gas pedal,
what is the reaction?
Ex. swimming
Ex. Running
Your Task – Choose one of the
following:
• Write a paragraph to explain an example
of each of Newton’s 3 Laws
• OR, Draw a picture to illustrate each of
Newton’s 3 Laws
• Now that I’ve given you a few examples, I
want you to think of one example of each
of Newton’s Three Laws of Motion from
sports.
Conservation of Momentum