Monday, February 16, 2009
♥ What is Terminal Velocity ?
Aristotle first recognized that falling objects fall at a constant speed. He probably came to this conclusion based on observations of things falling through water. Falling objects have two forces acting on them. The weight , acting downwards, the frictional drag rushing past, which tries to slow the body down. This drag force acts upwards and therefore lessens the acceleration as the body falls. If the body continues to fall, the acceleration will continue to decrease and at a certain speed, the drag force will just balance the weight, and the body will be falling at a constant rate. This rate is called the terminal velocity.
As long as the body is falling with a speed less than the terminal velocity, the weight force is less than the drag force, and the object will continue to accelerate. However, as the object gets close to its terminal velocity, the drag almost balances the weight and the total force on the body is small. and so the acceleration is also small. Thus, the body gradually approaches the terminal velocity.
The time it takes an object to reach terminal velocity depends on the speed it is travelling at, which depends on its weight. Therefore a light object will reach its terminal velocity pretty soon and requires a shorter distancethen a heavier object. Very heavy objects will reach their terminal velocity if they fall far enough. For example, we calculate the terminal velocity for the average person and find it to be around 80m/s. The a person will have to fall to reach his/her terminal velocity can be approximately judged using these principles. We know that as soon as the person exits the plane(for example, a skysurfer), his/her acceleration would be close to gravitational acceleration, around 9.8 m/s2. We also know however that his/her acceleration would gradually drop to zero as the speed increased toward 80m/s. Therefore, we can approximate that he/she would have to fall a good deal longer than 8 seconds.
3:37 AM
