Applying Bernoulli’s Principle
Bernoulli’s principle has many applications. One important application
is used in airplanes. Airplane wings can be shaped to take advantage
of Bernoulli’s principle. Certain wing shapes cause the air flowing
over the top of the wing to move faster than the air flowing under
the wing. Such a design improves the lifting force on a flying airplane.
Many racecars, however, have a device on the rear of the car that
has the reverse effect. The device is designed like an upside-down
airplane wing. This shape increases the pressure on the top of the car.
The car is pressed downward on the road, which increases friction
between the tires and the road. With more friction, the car is less likely
to skid as it goes around curves at high speeds.
A prairie-dog colony also shows Bernoulli’s principle in action.
The mounds that prairie dogs build over some entrances to their
burrows help to keep the burrows well-ventilated.
1
Air closer to the ground tends to move at slower speeds than air
higher up. The air over an entrance at ground level generally
moves slower than the air over an entrance in a raised mound.
2
The increased speed of the air over a raised mound entrance
decreases the pressure over that opening.
3
The greater air pressure over a ground-level entrance produces an
unbalanced force that pushes air through the tunnels and out the
higher mound entrance.
Bernoulli’s Principle in Nature
Bernoulli’s principle explains why having two entrances
at different heights helps ventilate a prairie-dog burrow.
2
The air over the raised entrance
moves faster and has less
pressure than the slower-moving
air near the ground.
1
Air moves more
slowly near
the ground.
3
The pressure difference
between the two
entrances moves air
through the tunnel.
Chapter 12: Gravity, Friction, and Pressure 421