Transcript Ch. 4-Newton`s 1st law

Exploding whales
Residents of Tainan learned a lesson in whale
biology after the decomposing remains of a 60ton sperm whale exploded on a busy street,
showering nearby cars and shops with blood
and organs and stopping traffic for hours. The
56-foot-long whale had been on a truck headed
for a necropsy by researchers, when gases from
internal decay caused its entrails to explode in
the southern city of Tainan. Residents and shop
owners wore masks while trying to clean up the
spilt blood and entrails. The whale had died on
Jan. 17 after it beached itself on the
southwestern coast of the island.
As it was during the peak of summer with
temperatures reaching over 100 degrees,
the beached whale had been rotting in the
heat for over 12 days until the explosion.
The excessive heat had caused the gases
within the whale’s digestive tract to expand
to the point that the thick blubber couldn’t
withstand the pressure and it exploded.
The intestines, blood, excrement, and other
fluids spread for a 2 block radius. Venders
were selling drinks and treats to curious
spectators are they watched the carnage.
Newton’s Laws of
Motion
Forces, Inertia, & Friction
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Force: a push or a pull; any influence that
tends to accelerate an object.
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Measured in Newtons (N)
Inertia: the property of a body to resist
change.
Friction: the force that acts to resist the
relative motion of objects or materials in
contact.
Newton’s First Law
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The law of Inertia
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Every object continues in a state of rest, or of
motion in a straight line at a constant speed,
unless it is compelled to change that state by
forces exerted upon it.
Things tend to keep doing what they’re
already doing.
Objects in a state of rest, stay at rest.
Newton’s First Law
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Forces are needed to overcome any friction
that may be present to get an object
moving.
Objects in motion, stay in motion.
Mass and Inertia
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Mass: the amount of matter present in an
object
The amount of inertia depends on an
object’s mass
The more mass, the greater the
inertia…and the greater the force it takes to
change the state of motion.
Mass and Volume
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Volume is a measure of space
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Mass is a measure of the amount of matter
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Measured in cubic centimeters (cm3) or liters (L)
Measured in kilograms (kg)
They are NOT EQUAL
Which weighs more…a pound of feathers
or a pound of lead? Which has more
volume?
Mass and Weight
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They are NOT the same thing!
Mass depends on the # of and kind of
atoms in an object.
Weight varies with location, based on
gravity.
Mass is the same everywhere; weight is
not.
Weight
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Weight is a force
It is measured in Newtons (N), just like
forces are.
A material that is 1 kg on Earth weighs 9.8
Newtons
W = mg
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Weight is equal to mass times the
acceleration due to gravity.
Net Force
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Net force: the combination of all forces acting
on an object.
It is the net force that changes an object’s state
of motion.
Equilibrium: what the net force is equal to zero.
If an object is resting on the table, the table is
pushing on it with the same force that the book
is pushing on the table.
Lab Activity
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You and your lab partners will simulate a
car crash for a passenger with AND without
a seat belt.
You will use only tape, string, a weight,
your book, a small crate, and a graduated
cylinder.
Lab Questions
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What stopped the motion of the “doll”
without a seat belt when the cart crashed
to a stop? Why?
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Was there any difference for the “doll”
with a seat belt? Why?