How air friction affect motion of object like car and bicycle?

Answer 1

Air friction is simply resistance. This friction is created when a mass moves against a stable force like air, and is the measure of force needed to allow movement. For an easy visual, try pushing a cube or a triangle through water. You will understand the principal of streamling as the means to minimize that friction affect.

When objects move on land, air particles are pushed away. This means more opposing forces against the moving object (in this case car and bicycles), reducing its speed, making it stop more quickly.
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Air Friction is the biggest enemy to the efficiency of any vehicle. Whenever one blows air over any surface then the surface experiences a shear force in the same direction trying to move plate with it. This is due to a property called viscosity of fluids, so even air which has very less viscosity has considerable effects. Similar thing happens when air blows over cars or even if air is still and car is running through it, then relatively air is moving over the car body. So the air will exert a shear force on the body of the car. moreover, if the shape of car's body is sort of a blunt shape, in simple terms like a very bulged body it will experience a form drag, in simple terms a force in the direction of flow due to pressure difference in the front and the back of car. This has a greater effect on performance of cars at high speeds so it is common to see that the car bodies are streamlined i.e. in simple terms shape like dolphins or what we call it ' a teardrop model'.
Air resists the motion of an object , the faster it is the more fricition there is . Aerodynamics is an independent part of science where people study the effect of air on objects in motion , thus the creation of more inclined surfaces and several geomatric shapes to reduce airi resistance.