Hobbies And Interests
Air Resistance and Velocity
Even when you walk, air resistance force works against you, albeit very gently. Because you are not moving very fast, you won't even notice it, unless it is a very windy day. When you run, however, even on a calm day, you notice the effects on your face as the air pushes against you and rushes by you. The reason is that as you speed up, the collision of atoms and molecules happens at a faster rate and with more force. This translates to the air resistance force getting bigger as the speed or velocity of the object increases.
Air Resistance and Mass
Only taking into account body size -- not athletic ability -- smaller people of the same age can usually run faster than larger people. The reason is the air resistance force. The faster an object moves, the more air resistance; similarly, the larger an object, the more air that object must displace to push through it. This means for a larger person running that he must not only overcome air resistance that the accelerated velocity causes, but he must also overcome additional air resistance due to his size and shape.
Air Resistance and Shape
Cars, buses, trains, airplanes and even boats must overcome air resistance in order to get people from point A to point B. Transport vehicles for obvious reasons are much larger than the average human and must move much faster to make it worth the time for companies to build them. Therefore transport vehicles must overcome much larger air resistance forces due to faster velocities and larger masses. To help accomplish this, manufacturers streamline vehicles in an attempt to reduce drag. This process, however, is never straightforward and often designs that seem worthy turn out to produce more drag. Usually such designs are modified continuously and subjected to multiple wind tunnel tests to improve efficiency.
Objects in the Air
For objects moving in the air, another force impacts air resistance: gravity. Gravity is constantly pushing things back toward the ground, while air resistance pushes up on the object. In most cases, the gravity force is much stronger than air resistance, and eventually the object hits the ground. For an airplane to counteract gravity, the plane must produce lift to keep it in the air and level. Planes accomplish this through the aerodynamic design of its wings, thereby making air resistance work for the plane.