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

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 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.

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).

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.

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).

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.

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.

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.

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.

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

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 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.

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.

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.

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

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).

"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.

"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.

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.

"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.

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.

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.

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.

"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.

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.

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.

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

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!

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."

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

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.

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.

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.

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!

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.