WHAT HAVE WE SEEN SO FAR?

A brief recap…

So far, we have looked at fluids and we have seen that fluids exist as both

liquid and as air.

FLUIDS

We have also seen how a fluid passes around an object.

Bernoulli noticed that pressure exists all around us. In fact, he found that

stationary fluids such as air and water exert pressure in

all directions.

BERNOULLI’S PRINCIPLE

Bernoulli also discovered that the faster air flows, the

less pressure it has.

Now, we are going to look at the force of LIFT and see

how it applies to flying objects such as airplanes.

FLYING WINGS

Airplanes stay in the air because of the shape of

their wings.

Imagine a wing without it’s

skin on

Imagine a wing flying fast through the

air

DIRECTION OF AIRPLANE

The special shape of a wing is called an airfoil.

An airfoil is flat on the bottom and curved on

the top.

BOTTOM

TOP

TOP

BOTTOM

DIRECTION OF AIRPLANE

How does a wing rise as air passes around it?

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

When air hits the front of the wing it splits up

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

The air flowing over the curved top of the wing has further to go than the air

going under the flat bottom of the wing.

Predict: How will both air molecules arrive at the tail of the wing at the

same time if the molecule on top has a farther distance to travel?

For the two streams of air to reach the back of the wing at the same time, the top stream must travel faster than the bottom. (It has a farther distance to

go.)

For the two streams of air to reach the back of the wing at the same time, the top stream must travel faster than the

bottom. (It has a farther distance to go.)

For the two streams of air to reach the back of the wing at the same time, the top stream must travel faster than the

bottom. (It has a farther distance to go.)

This fast moving air creates a low pressure area on the top of the wing

and a high pressure area on the bottom of the wing. (Bernoulli’s

Principle)

LOW PRESSURE

HIGH PRESSURE

Predict: What is our high pressure air zone going to do?

Why?

LOW PRESSURE

HIGH PRESSURE

Air will move from a high pressure zone to low pressure zone. As it pushes against the wing, lift is

created.

LOW PRESSURE

HIGH PRESSURE

UP

UP

UP

AND

AWAY!!!