Science and Math For Technology
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- Aerodynamic Forces Drag
- *Why is this true in both cases The answer is that air is a fluid [as well].
Rolling Friction Rolling friction is the resistive force that slows objects as they are rolling. Rolling friction has much less resistive force than sliding friction. Bearings with the least amount of friction are ball bearings or roller bearings. Ball bearings contain an inner groove called a race. An outer race traps the balls and holds them between the two races. The inner race also holds the axle or shaft. The roller bearing has even less friction than the ball bearing. This bearing contains small cylinders instead of balls.  
Aerodynamic Forces Drag is the resistance caused by the motion of objects through the air or water [in a fluid]. In most cases, drag is not favorable and causes moving objects to use more energy to continue movement. We cannot swin very fast because of hydrodynamic drag, which is drag due to the motion of a body in water. Air and water resist a body passing through it. *Why is this true in both cases? The answer is that air is a fluid [as well]. You experience aerodynamic drag when you hold your hand out of the window of a moving automobile. Drag increases as the velocity of a body increases. It becomes very important to reduce drag in automobiles and airplanes, because the drag force depends on the square of velocity, causing the vehicle to use lots of energy to keep going.   
Aerodynamic forces can be used to benefit people. Airplanes work because the shape of the wings cause a favorable force called lift. Racing cars use stabilizing fins to control steering. 
Two other factors are important when determining the amount of drag on an object. One deals with the physical size of the object; the other is the shape of the object. 
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