How Much Do You Really Know About the Science of Automobiles?

By: Jodi Compton
Image: Shutterstock

About This Quiz

The automobile is one of the triumphs of modern science -- a self-propelling machine that can carry, depending on its size and the strength of its engine, thousands of pounds of people and cargo, sometimes at very high speeds. The automobile uses two of the most important advances in engineering history: the wheel and the gear. These both preceded the car by centuries, but when the internal combustion engine was added to them, a whole new chapter in history was born. 

Of course, depending on who you talk to, this wasn't entirely a good thing! In parts of the world where automobiles are readily available and widely used, they are charged with contributing to air pollution, to rising obesity rates, and to deaths, injuries and disabilities. These claims, especially the one about death and injury from accidents, really can't be denied -- and they're a testimony to the darker side of automotive science. That is, many people are familiar and comfortable with cars without really understanding the physics involved in steering a 2,500-pound (or more) machine around at speeds o 55 miles an hour or more. Trust us, if a rigorous physics course was part of every driver's-education class, you'd see a drastic drop in texting while driving. 

Then there's the chemistry. Likewise, most people lightheartedly jump in their cars and drive them without considering that they are sitting mere feet from a machine that combines gasoline, oxygen and electricity from the moment the car is started up until the ignition is switched off. That, too, is pretty sobering!

Are you ready to test what you know about the science of automobiles? You'll never look at your car or truck the same way again!

Who formulated the three laws that govern many principles of driving?

One of the first things that physics students learn are Newton's First, Second and Third Laws. They're so important to cars and driving, we're going to break them out into their own questions.

Newton's First Law says that an object in motion ...

Newton declared that an object in motion remains in motion, and an object at rest remains at rest until acted on by another force. A lot of credit is due here: Newton formulated this law in a world with no actual experience of a vacuum, -- space exploration was still 400 years away. On Earth, there's always at least two "outside forces": gravity and air resistance. Newton was pretty perceptive to realize that these weren't actually constants.

Newton's Second Law is usually expressed as an equation: Force equals ____ times acceleration.

This explains why it's better to be hit by a Honda CRX going 30 mph than a Lincoln Navigator going 30 mph -- the difference in their masses. (Note: neither situation is ideal).

Newton's Third Law says that for every action there is an equal and _____ reaction.

This can be a little confusing, because sometimes the reaction does not appear opposite. If a car hits a trash can, the can will move in the same direction the car was traveling. But if the car hits a trash can full of lead, its front end would crumple and it would probably shudder backward a few feet -- because the lead-filled trash can transferred the car's energy back to it, in an "opposite" reaction. There are a lot of variables to take into account when predicting what will happen in a crash.

If you leave a can of Coke on the roof of your car, and it slides off when you peel out, this is because of ____.

Yes, the car is accelerating, but the can is not. It's at rest and remains at rest as the car slides out from underneath, because it's not being acted on by the same force the body of the car is (the thrust in the power train).

What is the name for the force of air resistance, which slows a car down?

Drag is a force that has to be taken into account any time someone designs and operates a vehicle. Not just a car -- your hear about "drag" a lot in aviation physics, too.

True or false: The only thing that holds the car down to the pavement is gravity.

OK, it's the main thing. But engineers can also create "downforce," which helps drivers keep all four wheels on the ground and stay in control at high speeds.

Which of these design elements creates downforce on the rear end of the car?

The spoiler is the raised, flat bar across the car's rear end. They're important to racing cars, but inevitably made their way into the consumer market as well, just because they look sexy.

At 40 miles per hour, how far will a car travel in 5 seconds?

We know: Nobody said there was gonna be math! But we're making a point: If you think it's harmless to look down at your phone to check a text message for five seconds at a moderate speed like 40 mph, consider that your car is going to cover 300 feet in those five seconds. It puts things in perspective.

What does engine oil counteract?

"Friction" and "heat" are obviously closely related. Specifically, engine oil prevents friction that would quickly destroy an unlubricated engine.

Which of these is NOT part of the four-stroke combustion cycle?

There's very little "rest" in the cycle, arguably none. The process goes intake (of mixed gasoline and air), compression (of the mixture), power (the ignition of the mixture) and exhaust (the gases leaving the cylinder). This process powers the up-and-down motion of the pistons, which is continuous.

The part of the car that absorbs force in a crash is called the ______.

The bumper or "fender" helps a little, but most of the work is done by the crumple zone, Technically, this is plural, "crumple zones," as there's one at the front and rear of the car.

True or false: In a collision with a fixed object, a car's driver can experience three times the g-force that an astronaut might at launch.

Astronauts experience about 11 g's. A car crashing into a fixed object can easily generate an opposite reaction of 20 or 30 g's, which is more than the human body can easily bear, and can cause internal injury.

How much g-force does a dragster commonly generate?

We've all felt an unpleasant jerk backward when an impatient driver makes a jackrabbit start from a stoplight. Trust us, it's a lot worse in a dragster, which is why racers are usually young and fit, despite not having to do anything actually athletic.

The kind of energy that cars have is called _____ energy.

"Kinesis" is the Greek word for "motion." When you study kinetic energy, you are studying things like cars, aviation, baseball, and so on.

The physics term for putting something in motion is called _____.

You'll see this term in the name of California's Jet Propulsion Laboratory, and sometimes in things that have nothing to do with physics. Movie reviewers tend to like it ("Propulsive storytelling!" et cetera).

Is automobile driving correctly called a form of "locomotion"?

"Locomotion" is any means of moving from place to place ("loco" is from the Latin "locus," meaning "place"). But with the advent of train engines being called "locomotives," the wider meaning fell out of use.

When a car is referred to as a "5-liter," what does that refer to?

"Displacement" means the volume of the fuel-air mixture the cylinders can take in and compress. The greater displacement, the more powerful the explosions in the cylinders, and the greater the motive force created.

Which of these is the term meaning "rotational force"?

If you've ever twisted your ankle, you've felt an uncomfortable amount of torque on a vulnerable joint. In a car, torque is involved in the turning of the wheels, the distribution of power to those wheels and a car rolling over under unsafe driving conditions.

Which of these is a correct definition of acceleration?

"Acceleration" is an important concept in driving, so much so that we call the gas pedal "the accelerator." Even if you are holding a steady speed, this can still be phrased in terms of acceleration: Your rate of change is zero.

Are speed and velocity the same thing?

Here's the fine print: In everyday terms, yes, they're interchangeable. In physics terms, no. Speed is scalar and velocity is a vector -- a distinction too complicated to go into here.

One unit of horsepower is ...

We're used to thinking of watts as a term only used in relation to electricity (thanks, lightbulb aisle!) But it is the standard SI unit of power.

About how much horsepower might a present-day sports car (production, not racing) have?

A sports car usually has at least 300 units of hp, and can go up to 600 or more (which can be dangerous, as it's hard to handle). Also -- if there's turbocharging in the mix, the horsepower can be lower without sacrificing performance.

True or false: Horsepower is a term only used in relation to automobile engines.

"Horsepower" is generally applied to engines, whether or not they're in cars and trucks. So you'll see it in relation to motorboats, as well as power tools.

What does it mean if an engine is turbocharged?

Turbocharging uses the combustion system's own exhaust to create extra compression in the cylinders. This leads to a more powerful explosion in the cylinder and to greater force being created.

Is turbocharging bad for the environment, compared to naturally-aspirated engines?

Turbocharging uses the engine's own exhaust to make it run more efficiently. In fact, Ford uses turbocharging in most of its EcoBoost engines, to provide smaller engines with minimal decrease in performance.

What invention allowed engineers to turn flammable liquids (e.g. gasoline) into combustible gases?

Carburetors mix gasoline and air into a combustible spray. It is then ignited in the cylinder.

The design of the carburetor uses which law of physics better known in aviation science?

Bernoulli's principle lays out an inverse relation between speed and pressure. In everyday life, you see this every time you block a hose nozzle with your thumb, causing the water to shoot out with greater force. In carburetion, the speed of airflow determines the amount of fuel drawn into the chamber. In aviation ... well, that's a subject for another quiz!

The average car emits about 9,000 grams of _____ per gallon of gasoline burned.

Yes, this is what people are talking about when they refer to a car's "emissions." It's led states like California to mandate emissions testing, or "smog checks."

True or false: It is possible to ignite certain types of fuel without an electric spark.

Sounds impossible, right? But this is how diesel engines work. They use a specific kind of fuel, which combusts with sufficient compression.

Specifically, the Bernoulli principle comes into play via the use of a ____ tube.

A Venturi tube is one with a narrowed section, through which fluid will move faster. The fluid in this case is air moving through the carburetor.

About when did scientists and engineers start working on an electric car?

Inventors and engineers tried a number of propulsion methods and fuels for the earliest horseless carriages; petroleum-based gasoline was by no means the clear choice. The first working electric vehicle was built in the 1880s.

The 18th-century car made by Nicolas-Joseph Cugnot was powered by ____.

Cugnot apparently didn't intend his steam-powered "fardier" for simple passenger use. It was designed to carry four tons of cargo, and was alternatively called a "steam dray," the name implying its use in hauling.

True or false: The first car was also responsible for the first car crash.

There are reports of Cugnot's steam-powered vehicle crashing into a brick wall and damaging it, but this might be apocryphal. You have to admit, it has a nice symmetry!

If you could drive a car at the speed of light, what would happen when you turned on the headlights?

This question is almost impossible to answer. If you're really interested, explore the debates around this question on the internet. It'll take time to really wrap your head around them, so we recommend having snacks and hydration close at hand.

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