Computing MPH

[bcroe at juno.com]

Steve,

You may remember from physics class,

Velocity = Acceleration X Time + the starting Velocity

That's for a fixed A, if it varies, you need to integrate.

V =  starting V + integral of A over time

Suppose you get a reading of A 100 times a second.
Take each reading (in feet/second squared) and multiply
it by the time (.01 second).  This answer is the change 
in Velocity  (in feet/second) during this 1/100 of a second.  
Add this to all the other changes in V (add a new one each 
1/100 second) plus the V before you started computing,
and you have the present V.  Adding the initial V is another
way of saying set the sum to zero before you start, if from
a standing start.

You don't have to compute in feet and seconds, but you
need compatible units to get the right answer.  I doubt 
your G meter reads out in miles/hour squared.  I'd convert
to MPH at the end; 88 feet/sec = 60 MPH.

Bruce Roe

On Mon, 27 Aug 2001 10:43:49 -0400 Steve.Flanagan at VerizonWireless.com
writes:

> He is using the RacePac data logger and it has a channel that shows 
> MPH.
> This is not based off the Drive Shaft or other but it uses the G 
> sensor.

> How would I go about figuring out MPH relative to G's?  

> What is the mathematics involved.  And does the Sampling rate of the 
> G
> sensor make a difference or are we just concerned about the average 
> G's and
> the time?
> 
> Thanks
> 
> Steve F
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