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Terminal velocity

When any object rises or falls through a fluid it will experience a viscous drag. As the object falls faster and faster the drag force increases. Eventually the drag force increases to a value where it is equal to the weight of the object and the body continues to fall at a steady speed. We call this the terminal velocity of the object.

At the terminal velocity viscous drag = Weight = mg

Large raindrops hurt much more than small ones when they fall on you - it's not just that they are heavier, they have a higher terminal velocity and so are actually falling faster.

People falling through the atmosphere will also eventually reach their terminal velocity. At low levels in the atmosphere (below about 3000 m) this is around 200 km/hour flat out and just over 320 km/hour head down. At high altitudes around 30 000m this can reach almost 1000 km/hour!

 
 
 
© Keith Gibbs 2010