Transcript Newton`s Laws of Motion

Newton’s
Laws of
Motion
To get us started….
Sir Isaac Newton
• Born in England
in 1643
• Lived for 85
years
Newton’s First Law
• An object at rest remains at rest, and
an object in motion remains in motion
at a constant speed and in a straight
line unless acted on by an
unbalanced force.
--Also called “The Law of Inertia”
What is this unbalanced force
that acts on an object in motion?
• There are four main types of friction:
• Sliding friction: ice skating
• Rolling friction: bowling
• Fluid friction (air or liquid): air or
water resistance
• Static friction: initial friction when
moving an object
Newton’s First Law
Examples of Newton’s
1st Law
a) A car suddenly stops and you strain
against the seat belt
b) When riding a horse, the horse suddenly
stops and you fly over its head
c) The magician pulls the tablecloth out
from under a table full of dishes
d) Lawn bowling on a cut and rolled lawn
verses an uncut lawn
e) A car turns left and you appear to slide
to the right
Newton’s Second
Law
• The acceleration of an object
depends on the mass of the
object and the amount of force
applied.
What does it mean?
If you place a force on an object,
1. It accelerates in the
direction…that you push it
2. If you push twice as hard…It
accelerates twice as much.
3. If it gets twice the mass…It
accelerates half as much.
Newton’s Second Law
Newton’s Third Law
• For every action, there is an
equal and opposite reaction.
Newton’s Third Law
Example #1:
Action:
Baseball
pushes glove
to the left
Reaction: ????
Example #1 Answer:
• The glove pushes the
baseball to the right.
Example #2:
• Action:
Bowling ball
pushes pin to
the left
• Reaction:
????
Example #2 Answer:
• Pin pushes bowling ball
to the right.
Example #3:
• Consider the
interaction depicted
below between foot
A, ball B, and foot
C. Identify the two
pairs of actionreaction forces. Use
the symbols "foot
A", "foot C", and
"ball B" in your
statements.
Example #3 Answer:
1. The first pair of action-reaction
force pairs is: foot A pushes ball B
to the right; and ball B pushes foot
A to the left.
2. The second pair of action-reaction
force pairs is: foot C pushes ball B
to the left; and ball B pushes foot
C to the right.
Challenge Question:
• Can you identify AT LEAST
FIVE sets of action-reaction
pairs in the picture?
Challenge Answer:
1. The elephant's feet push backward on the ground;
the ground pushes forward on its feet.
2. The right end of the right rope pulls leftward on the
elephant's body; its body pulls rightward on the
right end of the right rope.
3. The left end of the right rope pulls rightward on the
man; the man pulls leftward on the left end of the
right rope.
4. The right end of the left rope pulls leftward on the
man; the man pulls rightward on the right end of
the left rope.
5. The tractor pulls leftward on the right end of the left
rope; the left end of the left rope pulls rightward on
the tractor.
Some Real-Life Applications
of Newton's Third Law
1. An athlete executes a high jump by pushing against
the earth which, in turn, pushes him/her up in the
air.
2. We swim by pushing against the water, which
reacts, propelling us ahead.
3. A helicopter rises because of the reaction to the
downward push against the air produced by its
propellers.
4. Water of high pressure hoses leaves the nozzle
with great speed resulting in a thrust which pushes
the hose with such force that one person cannot
control it. Most people have experienced this to a
much lesser degree with the garden hose.
Quiz Time:
• Scenario #1
One foggy Christmas Eve, Santa's sleigh
was so heavily laden with gifts for the
good little boys and girls of LaVergne
that the jolly old fellow had to employ his
reserve reindeer, Clyde and Bubba, to
assist the other eight members of his
team. It took the combined force of the
ten powerful animals to pull Santa's
sleigh up into the starlit sky.
• Scenario 2
As Santa's sleigh was pulled
forward, faster and higher, a
little stuffed brown bear fell
undetected off the back of the
sleigh. Some little child is going
to be very disappointed.
• Scenario 3
Fortunately for LaVergne's children,
Santa and his team arrived on time.
Spying the first housetop, Santa
maneuvered his team for a landing.
Unbeknownst to him, the children who
lived there had left a treat on the roof for
Santa's reindeer. The reindeer saw the
treat and raced as fast as they could for
the yummy oats and berries. They
glided in, then they stopped so quickly
that Santa flew forward and bumped his
head on the front of the sleigh.
Obviously, he had forgotten to fasten his
seat belt!