The Ground Basics of Vehicle Physics



Physics is a tool of explaining the world; it is present in every area of our everyday lives, and no more so than our cars, bikes, and aeroplanes. Vehicles, from their fuel to movement to their repair, are the embodiment and a gift of physics. To truly understand how they work, the physical forces that they interact with and cause must be understood. These forces rely on sets of unbreakable natural laws that will be discussed below.


Firstly, friction is the mechanic force resisting the motion of solids and liquids across another surface or against each other. Friction, like all other physical properties, is governed by a set of basic rules, in this case calculated by French scientists Amotons and Coulomb. The first law of friction by Amontons describes that static frictional force is directly proportional to normal force, meaning that when the weight of an object increases, the frictional force working against the applied force also increases. Amontons’ 2nd law is that friction always acts against applied/normal force, while his 3rd and 4th laws state that friction isn’t proportional to the surface area of contact of an object, rather only the texture and roughness of the area of contact (if smooth in layout, frictional coefficient is low). The final law of friction by Coulomb states that kinetic friction is independent of the magnitude of sliding velocity (the speed of an object moving down a curve). There are two main forms of friction - static and kinetic friction. Static friction is the frictional force acting against static objects while kinetic friction tries to slow or impede moving surfaces. Within kinetic friction, there are sliding (solids sliding across each other), fluid (a solid moving against liquid pressure/friction), and rolling friction (a circular object rolling over a surface against friction).


Motion is the most omnipresent and basic action of nature. Although every object on Earth is undergoing motion, there are only three laws that govern it as found out by English physicist Issac Newton. Newton’s three laws of motion are as follows, the first being that an object will either remain static or move in a uniform line with constant velocity unless a force is acted upon it, the second stating that the greater the mass of an object, the more force needed to put it into motion (F=ma), and the final being that for every action, there’s always an opposite and equal reaction. Motion is also the main building block of the four forces of flight, thrust, drag, lift, and weight.


Finally, Bernouilli’s principle of fluid dynamics states that when air reaches a constriction, a narrowing, of the path it is flowing through, the speed and velocity of the air travelling through the constriction increases but the air’s pressure decreases. This change in pressure in the air’s path creates areas of low and high pressure, and this effect on air pressure helps vehicles when a part is located in a low air pressure area but is propelled forward faster by the internal energy of the external high pressure. This principle forms the basis of Aerodynamics, a subject used in the design of all vehicles and even certain technologies (e.g Windmills) to ensure speed, air resistance, and drag avoidance. Drag is air friction, something to be avoided, where the air molecules hitting a car try to slow down its speed. Some shapes are effective at avoiding drag, such as aerofoil, cones, and spheres, while other shapes contribute to the effect of drag, such as vertical rectangular/triangular prisms and cylinders. Additionally, walled-off or hole-type empty spaces can heavily contribute to drag. Air flow can become trapped and get stuck in these pockets of empty space, causing instability in the vehicle’s speed and movement. Other factors, such as inputting ballast weights in areas of a vehicle, can also be implemented to avoid drag, however the shape of the vehicle most determines how much of a detriment drag will be.




Citations

Aeronautics Guide Editors, “Aerodynamics and the Laws of Physics.” 9 Feb. 2020. Aircraft Systems Tech. https://www.aircraftsystemstech.com/p/aerodyna

Mics-and-laws-of-physics-law-of.html.


Benson, T. "Shape Effects on Drag." 12 June 2014. Glenn Research Centre - National Aeronautics and Space Administration. grc.nasa.gov/WWW/k-12/roc

ket/shaped.html


Editors of Encyclopaedia Britannica, "Newton's Laws of Motion." 3 Feb. 2020. Britannica. britannica.com/science/Newtons-laws-of-motion


Udegbunam, S. "The 5 Laws of Friction." 13 Oct. 2020. Afrilcate Creative Learning. https://afrilcate.com/laws-of-friction/