Transcript Aim: How do planes create lift?

Focus Point: How Do Planes
Create Lift?
March 30, 201

Instructional Objectives:

1. Explain how lift is
obtained.

2. Define the term
“airfoil”.

3. Discuss Bernoulli’s
Principle.
Can Air Act As a Force?
 Through
pressure, air
can exert a
force.
An example of air exerting a force
on a piece of paper:
Under normal
circumstances, if you
put a piece of paper
against your lower
lip, it will fall.
But …
PAPER
An example of air exerting a force
on a piece of paper:
When you blow
across a piece of
paper, the paper lifts
up.
PAPER
There must be a force pushing
the paper up:
The only way the
paper can lift up is if
the pressure below it
is higher than the
pressure above it.
Higher pressure
than on top
There must be a force pushing
the paper up:
The air pressure on top of the paper
must have gotten lower. Since the
only thing we did was make the air
on the top move, AIR PRESSURE
MUST DECREASE WHEN AIR MOVES.
Since we did not disrupt the air below
the paper, it has its normal pressure.
Bernoulli’s Principle

When the velocity of a fluid (air) increases
and it’s pressure decreases
Making air move quickly drops
its pressure.

In order to get a plane to fly, we need
to get the air on top of the wings to
move faster than the air under the
wing.
You and a friend running along
a straight surface
START
FINISH
IF BOTH ARE GOING THE SAME SPEED,
ONE WOULD LOSE IF ONE HAD TO
RUN AROUND SOMETHING.
START
FINISH
IF YOU WANT THE BOTH OF YOU TO GET TO THE
FINISH LINE AT THE SAME TIME…
START
FINISH
ONE MUST GO FASTER!
If this was air, it would also
have to move faster.
START
FINISH
If this was air, it would also
have to move faster.
START
FINISH
Making air move quickly
drops its pressure.
If this was air, it would also
have to move faster.
LOW PRESSURE
HERE
START
FINISH
Making air move quickly drops its
pressure.
What is an airfoil?

An airfoil is any surface designed to obtain a
desirable reaction from the air which it
moves. The airfoil converts air resistance into
a force useful for flight.
Wings
AIRFOIL
LOW PRESSURE
HERE
TYPICAL
WING
DESIGN
Making air move quickly
drops its pressure.
AIRFOIL
LOW PRESSURE
HERE
HIGHER PRESSURE
HERE
TYPICAL
WING
DESIGN
AIRFOIL
LOW PRESSURE
HERE
HIGHER PRESSURE
HERE
THE AIRPLANE LIFTS
OFF THE GROUND!
March 30, 201
SUMMARY – ACCOUNTABLE TALK
1) How does a plane achieve lift?
2) What is an airfoil?
3) What is Bernoulli’s Principle?