exponential function

Discussion in 'Physics & Math' started by kmguru, Jan 15, 2010.

  1. kmguru Staff Member

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    A good example of the exponential function is a car crash. One would think that a sixty mph crash would be twice as bad as a Thirty mph crash, but it’s not. According to the National Safety Commission, a crash speed of 60 mph versus a 30 mph represents a 100 percent increase in speed; however, it increases the crash forces by 300 percent.

    What is the math here?
     
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  3. prometheus viva voce! Registered Senior Member

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    I would guess that this is statistical. At x mph y% of crash victims are killed, and when you plot that on a graph you get an exponential(ish) line.

    What do you mean by "crash forces?"
     
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  5. kmguru Staff Member

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  7. AlphaNumeric Fully ionized Registered Senior Member

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    Its not exponential. It is quadratic.

    The kinetic energy of an object of mass m at speed v is \(\frac{1}{2}mv^{2}\). The KE of the same object at 2v is \(2mv^{2}\), which is 4 times as much. That's a 300% increase and if your brakes work with constant force it'll take 300% more distance to stop from speed 2v as it does at speed v.
     
  8. kmguru Staff Member

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    Thank you. It is those power functions that mess up people.
     

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