The name of this article comes from an iconic scene in one of the most famous movies ever made! James Bond, Agent 007 (or as he is known in the movie franchise, M) races his Aston Martin Vantage through the streets of Rome during the climax of Die Another Day. As he zooms down the highway at high speeds, he glances to his left and notices something strange.
A red Ferrari with Italian license plates is quickly gaining ground on him. It looks like the driver has caught onto what M does and is trying to outrun him with the same vehicle style and speed.
As the cars get closer to each other, you can hear the revs climb and then suddenly, both vehicles break into a full-on roar. You can also hear the squeal of the tires as they grip the road just enough to keep going.
When the cars come within close proximity, it becomes clear that the faster car will win the race every time. The Ferrari barely holds together after being overtaken by the more powerful Bentley. Only pieces of metal are left sticking out where there were once sleek curves and beautiful shapes.
The audience watches in awe as the Bentley explodes in a ball of fire. They also gasp when they notice that the now destroyed Ferrari still had its original roof panel. This shows how well insulated the vehicle was and why it survived the crash even though it lost part of its bodywork.
History of the mach number
The first recorded instance of someone doing a speed test with an average speed was in 1892, when Louis Dufour conducted his race at Issodef. He averaged 984 miles per hour (1 572 km/h) for one minute! This is now the current world record for fastest ever measured, beating his previous high of 1 128 km/h set just two years earlier.
It took another twenty-three more years before anyone repeated this feat again. In March 1905, Arthur Schindler ran a ten second pass which averages out to be 868 mph (1 441 kph). Eighteen months later in September 1906, Wilbur Wright did it twice! They both averaged 756 mph (1190 kph), setting new records that stand to this day.
These are some crazy numbers! It’s no wonder people are fascinated by fast cars and motorsports. It’s also why everyone loves watching Formula One racing, even if you don’t care about cars or track races.
The top speeds of any vehicle we know of can easily be calculated using what’s called the mach number. The mach number tells us how quickly the air would fly away from a solid object being moved through it at a given velocity. For example, let’s say there’s a boat traveling very slowly across water at a leisurely pace.
Compressibility effects
When it comes to speed, one of the biggest factors is compressibility. This refers to how much space there is in a vehicle due to air being displaced by things like wheels or other components.
If you were to take all of the material out of an empty car, what percent would be filled with air? This percentage represents the car’s “compressibility” or how easily it can be compressed down. A more dense object needs less room to fill up, meaning you have more freedom to go faster!
Most people are familiar with cars that seem to gain speed quickly before they get hit by something or pull over. That’s because when a vehicle gets going fast, momentum carries it forward first, and then gravity takes over as it drops. As it drops, however, the weight of the vehicle compresses the air inside it, so there is not as much space for it to expand in.
This effect decreases the amount of time it takes for the vehicle to drop, but it also requires more effort to push it away from whatever was hitting it, since there isn’t quite as much space for it to move in. The two work together, making it difficult to predict exactly where your vehicle will land!
Another way to think about this is that if the air in a vehicle was pure water instead of regular air, it would be completely fluid.
The effects of air resistance
While speed is an important factor in how fast you can achieve top performance, there are other things to consider. One of these is drag or friction caused by air as the vehicle moves through it.
As your engine gets faster, it needs more fuel to maintain its speed.
The effects of lift
Lift is an important term in aerodynamics that helps determine how fast your plane can fly. As you know, drag is the opposite of speed!
Lift comes from two main sources: pressure and induced momentum. Pressurized air acts like a cushion when the wing hits something, creating positive lift. Induced momentum occurs when the airflow moves faster than the surrounding area, which produces upward force or lifting action.
The greater the amount of lift, the faster your vehicle will travel. That’s why professional race cars are so sleek and thin; they need less drag to achieve top speeds!
However, too much lift can be a problem. When the car is traveling very quickly, the nose of the vehicle may hit the ground before enough forward momentum is built up.
The effects of gravity
When a rocket is traveling fast, it can reach infinite speed if you give it enough time. But as we discussed before, rockets are not indefinitely powerful, so at some point, they will run out of fuel and stop!
When a rocket reaches supersonic speeds, or travels faster than sound, its nose gets very hot. This is because there is no longer any cool air to conduct away heat from the engine, and the fuel burns extremely quickly, producing more energy per unit time.
As the rocket’s nose heats up, therefore, the air in front of it gets hotter and denser, which means that gravitational pull increases dramatically. An object with mass has an intrinsic natural tendency to attract other objects, and once again here, the heavier part pulls harder due to the increased density.
This increase in attraction is what causes the space surrounding the rocket to get tighter, like a fist getting squeezed. At high speeds this process happens much faster, making your average observer feel punched in the face when the ship breaks the sound barrier!
Note: There is another way to break the sound barrier that isn’t related to increasing atmospheric pressure, but instead lowering the effective weight of the vehicle. Learn more about How Fast Is Mach 10
Understanding mach number
The only thing that matters when it comes to speed is how fast you are going!
If we look at our car example, what does fast mean? It means faster than someone else! If I go twice as far as you, then I am moving two times as fast as you are because I’m traveling 2 miles per hour more than you every second of the time.
That doesn’t make sense so let’s rephrase that. If you were walking down the street and I was running after you, I would be around one and a half times as fast as you would be if I caught up with you!
This concept- which we will refer to as the ‘Mach Number’- applies to all objects in space, not just cars. An object whose relative velocity is equal to the speed of another object is referred to as being at the same mach number as the other object.
For instance, an airplane flying close behind a passenger jet has a higher mach number than the passenger jet since they both have a common destination but their individual speeds differ. When two vehicles enter into a head-on collision, the vehicle with the lower mach number usually wins due to drag. This is why planes always win in air battles!
The definition of the mach number depends on the units used, so make sure you understand those before trying to work out yours.
Calculating mach number
The easiest way to determine how fast you are traveling is by finding your current speed and multiplying it by 1,000.
Your speed can be found using either an electronic device or a camera. An easy way to find your current speed is with a GPS system in your car! If you don’t have one of these, use a handheld laser rangefinder or estimate your own average vehicle speed per mile-way home.
Once you have determined your current speed, multiply this value by 1,000 to get your mach number.
The faster you travel, the higher the mach number becomes.
Examples of mach numbers
The next step in finding your car’s ultimate speed is to compute what we refer to as its “mach number.” A mach number is simply a way to compare how fast you are traveling relative to the air that is moving past your vehicle, and thus how quickly you are going!
A common mistake when computing this value is assuming that the faster you go, the higher the calculated mach number will be. However, since velocity equals mass times acceleration, having a faster car does not mean that you can go any faster!
Your mach number depends on both your speed and the densityof air, which varies depending on the type of area you are driving in. Because of this, there is no standard definition or formula for determining what a high mach number is.
However, general rules of thumb say that a small, dense stream of air is given a higher mach number than an empty space with thinner air.
