Transcript Explain Archimedes* Principle.

Archimedes’ Principle states that a fluid will
exert an upward buoyant force on any object
that is in the fluid. This buoyant force is equal
to the weight of the fluid displaced by the
object.

A boat that is made of aluminum can float in
water because of the shape of the boat.
Since it is hollow, air fills most of the volume
of the boat, making the boat’s overall density
less than that of the water, therefore it will
float. Archimedes’ Principle tells us that the
upward buoyant force is equal to the weight
of the water the boat displaces.

When you walk in shallow water, a small
buoyant force pushes up on you (b/c you are
displacing a small amount of water), so most of
your weight is supported by your feet—OUCH!
When you walk in deep water, a large buoyant
force pushes up on you, so a lot of your weight is
supported by the water and less is supported by
your feet—AAAHH! Archimedes’ Principle tells
us that the buoyant force is equal to the weight
of the fluid displaced by the object.

A helium balloon will float into the sky
because the density of the balloon and
helium is less than the density of the air.
There is an upward buoyant force on the
balloon that is greater than the weight of the
balloon, so it rises. This buoyant force is
equal to the weight of the air that is displaced
by the balloon, according to Archimedes’
Principle.

Pressure is the amount of force exerted per
unit of area. Pascals are the SI units for
describing pressure. The equation for
calculating pressure is:
P = F/A
A = L xW
A = (7m)(8m) = 56 m2
F=PxA
F = (101,000 Pa)(56 m2)
F = 5.656 x 106 N

Bernoulli’s Principle states that as the velocity
of a fluid increases, the pressure exerted by
the fluid decreases. In other words, if a fluid
is moving (like flowing water or wind), then
that fluid pushes with less force than a fluid
that is moving slower or not at all.

Viscosity is a fluid’s resistance to flow.
Examples of fluids with high viscosity are
honey, syrup, lava, molasses.

It is dangerous to stand near train tracks when a
fast-moving train goes by because the train will
cause the air right beside it to move fast also. As
Bernoulli’s Principle states, as the velocity of a
fluid increases, the pressure exerted by the fluid
decreases. This means that there will be a low
pressure in the fast-moving air right near the
train. If you are standing there, then the higher
pressure behind you (because that air is not
moving as fast as the air in front of you) could
push you toward the train and you could get
seriously hurt!

An airplane’s wing is curved on top and flat on
the bottom, so that when the plane moves
through the air, the air moving over the top of
the wing goes faster than the air going under the
bottom of the wing. Bernoulli’s Principle states
that as the velocity of a fluid increases, the
pressure it exerts decreases. This means that
there will be low pressure above the wing and
higher pressure below the wing. This results in
an upward lift force which lifts the plane up.

When a stream of fast moving air is sent
between 2 empty pop cans, a region of low
pressure is created between the cans
according to Bernoulli’s Principle. Since the
air on the outsides of the cans is not moving,
it is at a higher pressure and will push each
can toward the middle.

Pascal’s Principle states that the pressure
applied to a container of fluid is transmitted
equally and undiminished throughout the
fluid and in all directions. In other words, if
you squeeze a plastic bottle of water, you will
increase the pressure of the fluid. This
pressure increase is felt throughout the entire
bottle of water, on all the inner sides of the
bottle.

When you suck on one end of a straw, you
decrease the pressure inside the straw. The
liquid (drink) is exposed to this low pressure
region inside the straw, but is also exposed to
the atmosphere outside of the straw. Since
the atmospheric pressure is greater than the
pressure inside the straw, the pressure from
the atmosphere pushes the liquid up the
straw and into your mouth.

A cup is completely filled with water (NO AIR BUBBLES!)
and then an index card is placed over the mouth of the
cup. When the cup is turned upside down, the card stays
over the opening of the cup, holding the water inside. This
occurs because inside the cup, there is about 1-2 pounds
of force (the weight of the water inside) pushing down on
the index card. Since all the air has been forced out of the
cup, there is no atmospheric pressure acting on the inside
of the card. On the outside of the card, the atmosphere
pushes on each square inch of the card with about 15
pounds of force. So if the cup opening’s area is about 7
square inches, there is a force of about 105 pounds
pushing up on the card. Since this upward force is much
greater than the downward force of gravity, the card does
not fall off.

Boyle’s Law states that as the volume of a container of
gas is decreased, the pressure of the gas increases, as
long as the temperature of the gas does not change. For
example, if you squeeze an inflated balloon (decrease its
volume), the pressure inside the balloon will increase, and
the balloon may pop. Charles’ Law states that as the
temperature of a container of gas increases, its volume
increases, as long as the pressure of the gas does not
change. For example, if you place a sealed, air-filled 2liter pop bottle into a freezer (decreasing the air’s
temperature), the bottle will crumple inward, decreasing
its volume. G-L’s Law states that as the temperature of a
gas increases, pressure increases, as long as the volume
does not change. EX: putting spray can in fire = BOOM!