Drag • Downforce • DRAfting - NASCAR Acceleration Nation

GRADES 5–7
Drag • Downforce • DRAfting
An Aerodynamics STEM Learning Guide
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the Three Ds of Speed!
The
3D
s
of
Speed
During a NASCAR race, race cars can reach speeds of more
than 200 miles per hour! Races are won—and lost—by
just fractions of a second. To be the first across the finish
line, drivers rely on three key aerodynamic features: drag,
downforce, and drafting.
DraG
As a race car zips along the track, it experiences drag, or air resistance.
Air pushing against the car as it moves causes it to lose speed. To
fight this slowing force, designers work to create cars that are more
streamlined so air flows easily around them.
Downforce
Race car drivers rely on downforce to help their cars firmly grip the
track. Downforce occurs as air moves under the car faster than it does
over the top. The slower air on top creates an area of higher pressure
above the car that pushes it downward. This provides more traction to its
tires and gives the driver better control while steering.
Drafting
During a race, drivers can get a speed boost by lining up their race cars. This is a
formation called drafting. When cars draft, the leading car blocks the movement of
air, creating low pressure behind it. High-pressure air moves forward to fill the space
between cars, tugging the trailing car forward while reducing the leading car’s drag.
As a result, both cars reach higher speeds.
Drag
Explore the science
of aerodynamics.
downforce
slow-moving air:
high pressure
fast-moving air:
low pressurE
DRAG
94
DRAG
ACTIVITY
Drop a flat sheet of paper from a height of about 3 feet
while a friend times how long it takes to hit the floor.
Now crumple a sheet of paper into a ball and repeat the
experiment. Did you notice how the object’s shape affected
how it moved through the air?
The flat sheet of paper met resistance and moved slowly.
Crumpling it into a ball reduced its surface area, so the
second sheet dropped to the ground faster than the first.
drafting
Learn how NASCar drivers use
drafting to race ahead of the pack.
Drafting Stage 1:
94
94
62
62
Low pressure between the cars pulls the trailing car forward
slow-moving air:
high pressure
fast-moving air:
low pressurE
Drafting Stage 2:
94
94
Both cars go faster
62
62
NASCAR drivers try to strategically improve the performance of their
vehicles using the Three D’s of Speed. One technique they use is
called drafting - where race cars closely line up one behind the other
to gain a boost in speed on the track.
When race cars draft, the leading car blocks the air, creating an area
of low pressure behind it. At the same time, low pressure also pulls
the trailing car forward toward the leading car. This pushes the highpressure air over the lead car’s spoiler, reducing its drag. The result
allows both cars to go a few miles per hour faster.
Try this quick trick to visualize drafting: take two marbles to your
kitchen sink. Run the water from the tap. Hold one marble under the
running water - and then hold the second marble under the first. See
how the second marble gets less wet because more water is blocked
by the first? Imagine that the water is air and you’re on your way to
understanding drafting in NASCAR racing.
downforce
DISCOVER THE SIMILARITIES BETWEEN
RACING AND FLIGHT THROUGH
AERODYNAMICS.
NASCAR race cars rely on a key element of aerodynamics – air pressure
– to stick to the track. Air pressure is a force caused by the weight of air
molecules pushing against an object’s surface. The shape of a plane’s wing,
also called an airfoil, works with the opposite combination of high and low air
pressure.
The splitter on top of a NASCAR race car forces fast-moving air underneath
the car and the skirting prevents slow-moving air from slipping underneath
the sides of the car. Fast-moving air causes low air pressure and slow-moving
air creates high air pressure. The combination of high pressure above and low
pressure below pushes the car down so it stays on the track.
ACTIVITY
Hold the short end of a sheet of paper with your hands
pointing up. Blow forcefully over the curve of the paper.
Check it out: faster-moving air over the top of the paper
creates lower pressure above and higher pressure below.
That creates lift, causing the paper to rise.
ext, fold a 1-inch flap along the short edges of the
N
paper.Turn the paper over and fold another 1-inch flap
on each edge. Sit the paper on a tabletop so that there is
a tunnel you can blow through. Blow forcefully through
the gap. Faster-moving air below the paper creates an
area of low pressure below and high pressure above. This
creates downforce, causing the paper to sag.
discovering drafting
Winning a NASCAR race requires more than a
super-speedy car. Drivers also use a strategy called drafting to get
ahead on the track. Read the passage below to learn about the technique’s
accidental discovery. Then answer the questions on the right.
The Discovery of Drafting
hat was the central idea of the text?
1 W
In 1960, racecar driver Junior Johnson was gearing
up for the second ever Daytona 500 race. But he
realized he had a problem. His car was much slower
than those of the top contenders in the race.
A
During a practice run, Johnson noticed that when
he pulled up close behind a faster car his vehicle
sped up, too. By the final lap of his run, he’d built
up enough speed to overtake the other car. Johnson
had discovered drafting.
D
Drafting occurs when a car lines up right behind
the car in front of it, with just inches between
their bumpers. Leading cars block the flow of air,
creating an area of low pressure behind them. This
area acts like a vacuum, sucking the trailing cars
forward. The trailing cars push high-pressure air
over the leading cars’ spoilers, reducing their drag
and also giving them a boost. The more cars that
are grouped in a drafting formation, the faster they
all will go.
B
C
Drafting is a common strategy used
in NASCAR races.
Drafting was first used by accident.
By driving close behind other cars,
racecars can move faster.
A car doesn’t have to be the fastest
to win a race.
he purpose of the third paragraph is to:
2 T
A
B
C
D
explain
the science of how
drafting works
describe the first time that drafting
was used in NASCAR
detail how drafting has changed in
the last 40 years
list the pros and cons of drafting
hat is a synonym for the word tactic?
3 W
A
B
ability
formation
C
D
idea
strategy
Using the drafting tactic, Johnson won the Daytona
500 even though his car wasn’t the fastest on the
track. Today, drafting is a common strategy in
NASCAR races.
1. D, 2.A, 3. D
ANSWEsS:
Kn
Test your
KnowlEDGE
hat does the science of aerodynamics
1 W
study?
A
The weight of objects
he speed and flight of objects
T
The movement of air
The sound of air
B
hat are three key aerodynamics
2 W
C
principles?
Drag,
height, and acceleration
Drag, downforce, and drafting
Acceleration, downforce, and motion
Acceleration, height, and motion
hat word describes a force that slows
3 W
D
he goal of adaptations to NASCAR
9 T
racecars is:
A
an object when air pushes against it?
B
A
B
C
rag
D
Downforce
C
D
Drafting
Deceleration
hat aerodynamics force is used to
4 W
create both lift and downforce?
A
B
ir speed
A
Air pressure
C
D
Both A and B
N
either A nor B
rue or false? Downforce is caused by
5 T
D
E
hy is the science of aerodynamics
10 W
important to racing?
the combination of high air pressure
pushing against the top of an object and
low air pressure beneath an object.
A
A
B
True
B
False
rue or false? Downforce is the opposite
6 T
of lift.
A
True
B
False
C
rue or false? Drafting is a driving
7 T
strategy that improves speed.
A
True
B
False
prevent racecars from flipping over
To
or lifting.
To provide more downforce to improve
tire traction.
T
o force high-pressure air over the car
to make sure it “sticks” to the track.
To create more contact between the
tires and the tracks.
All of the above
D
ecause aerodynamics helps improve
B
the safety of the racecars, keeping
them on the track.
Because aerodynamics helps enhance
the speed of the racecars, helping
drivers zoom past the competition.
Because aerodynamics helps
improve the performance of the cars,
keeping them running smoothly and
consistently.
All of the above
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ANSWEsS:
A
B
C
D
wo or more racecars accelerate
T
next to each other with inches
between them.
Two or more racecars line up,
one behind the other, with inches
between them.
Two or more racecars tap the
bumpers of the cars in front of them.
None of the above
1. C; 2. B; 3. A; 4. B; 5. A; 6. A; 7. B; 8. B; 9. E; 10. D
A
B
C
D
rafting happens when:
8 D
RACECAR
ADAPTATIONS
Each racing season, NASCAR sets rules that determine the shape and
weight of its cars. Check out some NASCAR racecar principals and
learn how they influence safety, speed, and racing aerodynamics.
1 Spoiler
This device traps high-
pressure air, creating
downforce to provide more
rear-tire traction. It also
increases drag to prevent
racecars from traveling at
unsafe speeds.
Strips
2 Roof
These thin rails run
along the roof edges
to disrupt airflow
and cut down on
unwanted lift.
Flaps
3 Roof
These spring open if
the car starts to slide
or spin. They disturb
air moving over the car,
reducing lift so the car
doesn’t go airborne.
4 Skirting
Edging around the bottom
of the car prevents highpressure air from moving
under the vehicle and
creating unwanted lift.
If the car starts to slide
sideways, the skirting
lessens the chance of the
car spinning or flying off
the track.
5 TIRES
Treadless tires
make more contact
with the ground,
increasing traction.
6 SPLITTER
This flat strip runs parallel
to the ground underneath
the front bumper. Air
accelerates more quickly
under the splitter, leading
to a low-pressure area
that helps suck the car
downward toward the track.