Two cars clocked at 200 km/h on Martin Grove
07-19-2009, 12:55 PM
#16
Racer
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7 seconds is a long time, but I think what they were attempting to do was to let us know what the stopping distance is of a car doing 200mph.
200mph equates to about approximately 300 feet. Does anybody here now of anybody on the streets that leaves a minimum of 300 feet between vehicles? How about other objects that pop out of nowhere in front of you. It does happen.
200mph equates to about approximately 300 feet. Does anybody here now of anybody on the streets that leaves a minimum of 300 feet between vehicles? How about other objects that pop out of nowhere in front of you. It does happen.
The measure of velocity is distance divided by time (fps), stated as feet per second. The measure of acceleration (or deceleration in this case) is feet per second per second. That assumes a reasonably good co-efficient of friction of about .75; better is .8 or higher while conditions or tire quality might yield a worse factor of .7 or lower.
No matter the velocity, that velocity is reduced 15 fps every second. If the initial velocity is 60 mph, 88 fps, after 1 second elapsed, the vehicle velocity would be 73 fps, after 2 seconds it would be 58 fps decreasing progressively thereafter. For the true mathematical perfectionist (one who carries PI to 1000 decimal places), it would have been technically correct to indicated the formula is 'fpsps' rather than 'fps', but far less understandable to most drivers. Since at speeds of 200 mph or less, the difference from one method to the other is in thousanths of seconds, our calculations in these examples are based on the simple fps calculations.
Given the previous set of conditions, it would mean that a driver could stop the described vehicle in a total of 6.87 seconds (including a 1 second delay for driver reaction) and your total stopping distance would be 302.28 feet, slightly more than a football field in length!
No matter the velocity, that velocity is reduced 15 fps every second. If the initial velocity is 60 mph, 88 fps, after 1 second elapsed, the vehicle velocity would be 73 fps, after 2 seconds it would be 58 fps decreasing progressively thereafter. For the true mathematical perfectionist (one who carries PI to 1000 decimal places), it would have been technically correct to indicated the formula is 'fpsps' rather than 'fps', but far less understandable to most drivers. Since at speeds of 200 mph or less, the difference from one method to the other is in thousanths of seconds, our calculations in these examples are based on the simple fps calculations.
Given the previous set of conditions, it would mean that a driver could stop the described vehicle in a total of 6.87 seconds (including a 1 second delay for driver reaction) and your total stopping distance would be 302.28 feet, slightly more than a football field in length!
07-20-2009, 12:53 AM
#17
Burning Brakes
7 seconds is a long time, but I think what they were attempting to do was to let us know what the stopping distance is of a car doing 200mph.
200mph equates to about approximately 300 feet. Does anybody here now of anybody on the streets that leaves a minimum of 300 feet between vehicles? How about other objects that pop out of nowhere in front of you. It does happen.
200mph equates to about approximately 300 feet. Does anybody here now of anybody on the streets that leaves a minimum of 300 feet between vehicles? How about other objects that pop out of nowhere in front of you. It does happen.
150 ms or less is doable.
07-20-2009, 05:18 AM
#18
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Whether it takes 1 second or .1 second to react, that car needs about 300 feet to stop. A lot can happen in 300ft.
07-21-2009, 10:02 PM
#20
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There are a couple of things I noticed about the stopping debate.
First, 200 KPH was originally mentioned, then 200 MPH crept in.
200 MPH is another kettle of fish entirely – stopping distance in a test in Car and Driver in Feb 2008 ranged from about 1100 feet up to 1700 feet, taking between 8 and 11 seconds.
The decel rate ranges from 0.84 to 1.15 G, or between 27 and 37 feet per second per second.
At more reasonable speeds:
Road & Tracks GT3 RS test showed 115 feet from 60 and 193 feet from 80 – just over 1G. Stopping from 60 would take 2.6 seconds; from 80 – 3.5.
Extrapolating, a GT3 RS should stop from 200 KPH in 5.3 seconds, taking 475 feet.
As a point of reference, a Subaru WRX STI stops from 70MPH in 160 feet, taking 3.1 seconds, generating 1 G decel rate.
First, 200 KPH was originally mentioned, then 200 MPH crept in.
200 MPH is another kettle of fish entirely – stopping distance in a test in Car and Driver in Feb 2008 ranged from about 1100 feet up to 1700 feet, taking between 8 and 11 seconds.
The decel rate ranges from 0.84 to 1.15 G, or between 27 and 37 feet per second per second.
At more reasonable speeds:
Road & Tracks GT3 RS test showed 115 feet from 60 and 193 feet from 80 – just over 1G. Stopping from 60 would take 2.6 seconds; from 80 – 3.5.
Extrapolating, a GT3 RS should stop from 200 KPH in 5.3 seconds, taking 475 feet.
As a point of reference, a Subaru WRX STI stops from 70MPH in 160 feet, taking 3.1 seconds, generating 1 G decel rate.
07-21-2009, 11:47 PM
#23
