HOW STUFF WORKS
QUIZZES

The Car Aerodynamics Quiz
by Staff
Fire up the wind tunnel and get ready to answer 30 questions about the many ways air flow affects the performance of cars on highways and speedways. Spoiler alert!

### The term used to define and measure the air resistance acting against a moving car is…

• coefficient of drag
• lemniscate of Bernoulli
• frictional eigenvalue

### Imagine a moving car. The area directly in front of the car is an area of…

• lower air pressure
• higher air pressure
• a perfect vacuum

### What happens when air struggles to fill the void left behind a car that's moving forward?

• The low pressure area behind the car &quot;pulls&quot; on the car, creating drag.
• The air rushes into the void and pushes the car forward.
• The low pressure area creates lift that reduces the traction of the rear tires.

• turbulence
• resistance
• drafting

### What is it called when air molecules break away from the car's surface and become turbulent?

• flow separation
• delamination
• the Venturi effect

### What is the name for the layer of air molecules that forms along the surfaces of a moving object, such as a car?

• viscosity layer
• boundary layer
• diffusion layer

### Which part of a car's bodywork helps create an area of low pressure underneath the car?

• windshield
• rear spoiler
• front splitter

• round
• oval
• square

### Along with coefficient of drag, the most important aerodynamic aspect of a car's shape is…

• frontal area
• height
• roof curvature

### The best shape for a car's rear window is…

• a flat panel that angles in toward the passenger compartment
• a flat vertical panel

### What helps create an area of high pressure over a car's trunk, negating the low pressure created by the rear window?

• a wing
• a spoiler
• brake cooling vents

### Does a wing on a race car act the same as a wing on an airplane?

• Yes, but a wing on a car is inverted to provide downforce instead of lift.
• No, it's a misconception that they perform similar functions because they were given similar names.
• Yes, but other parts of the car's design must work to overcome the lift created by the wing.

### Which of these does NOT help create low air pressure underneath a car?

• a raked angle, with the front of the car closer to the ground than the rear
• ram air intake on the hood
• side skirts

### Why does the trailing car gain speed when "drafting" another car (or truck)?

• It's riding the wave of turbulence created by the lead car.
• It's driving in the low pressure area created by the lead car and therefore doesn't have to push through as much air.
• The flow separation from the lead car pushes more air into the trailing car's engine, increasing the horsepower.

### A wing with an aggressive angle of attack generates both downforce and…

• lift
• drag
• the Venturi effect

### NACA ducts can be used to reduce what?

• lift
• frontal area
• the size of the boundary layer

### What does a rear diffuser do?

• seal off the area beneath the car, keeping all air flow out
• expand the area under the car, accelerating the movement of air out from under the car, increasing downforce.
• dissipate turbulence from the wheel wells

### As a car's velocity doubles, what happens to the amount of drag it experiences?

• It remains the same.
• It increases ten times.

### What is a potential problem when a race car drafts another car very closely?

• reduced fuel efficiency
• over-revving the engine
• overheating

### To minimize drag, elements that project from the main body of the car, like mirrors, should be placed…

• very close to the main body
• as far from the body as is practical
• in front of a wing or spoiler
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