Air Exerts Pressure

1. Air is like a fluid and it takes up space.
2. Air has weight.
3. Air exerts pressure.
4. The Earth’s atmosphere is made up of
many different gases.
5. Air can be compressed.
Air Takes up Space
#1 Capture air inside of a bag.
 #2 The water stayed in the funnel because
the air takes up the space inside the bottle.
 #3 The tissue didn’t get wet because the air
takes up the space inside the cup.
#4 The balloon could not be blown up
because the air inside the bottle is already
taking up the space.
Air Has Weight
#1 By putting the newspaper on top of the
meter stick it increased the surface area for
air to sit on therefore increasing the weight.
#2 When one of the balloons popped the
other dropped because of the weight of the
air inside the balloon.
Air Exerts Pressure
#1 The air pressure pushing upward on the index
card is greater than the force of gravity pulling the
water down.
#2 Another reason why the tissue didn’t get wet is
because the air inside the glass was exerting
pressure against the water not allowing it to enter.
#3 A)When the balloon is filled up it is exerting
pressure on the walls of the balloon. B) When the
balloon was let go the pressure inside the balloon
propelled the balloon forward (Newton’s 3rd Law)
A change in temperature will change
air pressure.
Atmospheric (air) pressure – is
measured with a barometer.
 Film Canister Rockets
The more tiny air particles there
are above a place or object the
higher the air pressure.
(Stack of Books Analogy)
1. Measures atmospheric pressure
2. Indicates the height of a place above sea- level
3. Used for weather prediction, as high air pressure in
a region indicates fair weather while low pressure
indicates that storms are more likely.
Air is a fluid and is capable of being
 Why can it be compressed?
 Where do we see or use compressed air??
 Balloons
 Basketballs / Footballs / Soccer Balls
 Bike and Automobile Tires
1. The more oxygen a fire gets the more it
2. If you stoke a fire with a stick or blow on
the hot coals or burning wood it will burn
more. This is because you have let more
oxygen into the fire.
1. Water vapor is also an ingredient of air.
2. Damp air will effect metals. – it will
change their colour (brown) and they
start to rust.
3. Rust will form CORROSION and overtime
the rust will destroy the metal
4. We have a lot of rust in Canada because
of our damp climate
1. In all animals, gaseous
exchange takes place through
lungs or gills.
2. Oxygen is taken in and carbon
dioxide is given off.
The particles in air are always moving.
Air like a fluid will always move from a high
pressure area to a low pressure area
3. Bernoulli’s Principle
Daniel Bernoulli – Swiss scientist and
He studied how water and air flow.
It was through this principle that we
understand why birds and airplanes can fly.
• When air rushes past the wing of a plane, it
flows above and below the wing.
• The top part of the wing is rounded and the
bottom is fairly straight.
• Therefore, air rushing over the top of the wing
has to travel a greater distance to the back of the
wing compared to the bottom.
• As a result, the air on the top of the wing has to
travel faster to keep up with the air underneath.
• This creates a low pressure area on the top of
the wing.and high pressure area on the bottom.
• The difference of pressures on the surfaces of
the wing create LIFT (the upward force that
keeps planes and birds aloft.)
What are some of the similarities in design
between the airplane compared to birds?
 Streamline
/ Aerodynamic design
 Wings / Wings or Airfoil
 Landing gear / Legs
 Tail / Rear wing (stabilizer)
 Any others?
Cool Characteristics of
Two important things that birds have that
help them keep their weight low are:
1) Feathers – are light, flexible, used for
protection and also to keep the bird warm.
 2) Hollow bones – are very light
Forces on an Airplane
Forces that act on birds during
1) Lift – the force that pushes upward, created by
the movement of air over and under the wings.
 2) Drag – the force of the air pressing against the
bird and slowing them down.
 3) Weight (gravity) – the force that pulls the bird
 4) Thrust – the force that moves the bird forward,
caused when a bird flaps its wings.
What is Propulsion?
It means to push forward or drive an object
 A propulsion system is a machine that
produces thrust.
Now lets take a look at how airplanes and
animals fly…or propel themselves.
• Thrust – a force which can cause an object to move
in a direction. (Eg. Balloon Rocket)
- Thrust often comes from muscles or engines.
• Newton’s Third Law
– For every action (in this case,
air escaping the balloon) there is an equal
and opposite reaction (the balloon is
propelled forward).
Push - the movement an animals
wings make.
They push against the air.
•Propellers – blades which are
turned at high speeds
- Eg. Helicopters or
In order for devices or
living things to fly:
must have sufficient lift
to overcome the downward
force of gravity.
Parachutes are designed to
create _______
Air Resistance so that
they fall slowly to the earth.
 The larger the Parachute, the
slower it will fall to the earth.
 Which other force affects the
parachute? _________
 Which force is greater?
Making an object streamline
or aerodynamic:
Streamline: a shape designed to have as little air
resistance or drag as possible.
How can you make an object more streamline?
1) Round edges
2) Slope surfaces
3) Smooth out surfaces
4) What else??
Race cars:
Race Boats:
Canadian Geese:
Bad examples of Streamlining:
 Using
only one piece of paper,
design an object that is very
streamline or aerodynamic.
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