View Full Version : Physics wizards! -- how to convert to braking g-force?
Steve1968LS2
11-19-2007, 12:38 PM
Ok.. I can't find the formula for this.
If a car stops from 60mph to zero MPH in 116 feet how many g-forces (negative) did the driver experience?
I do know that 60mph is 26.84 meters per-second and that the car weighs 3140 with driver (1424.28 kilograms)
Help a brotha out!
Fuelie Fan
11-19-2007, 01:35 PM
v^2 = v_i^2 + 2ad
you want a
a= (v^2-v_i^2)/2d
60 mph = 88 ft/s
a = (0-88^2)/(2*116)
a = 33.4 ft/s^2
1g = 32.2 ft/s^s
"G's" = a/g = 1.04
NOTE: this is an AVERAGE value over the entire stop. The driver most likely experienced higher peak forces. It would be easy to pull from a data log of speed vs time since a = dv/dt
jannes_z-28
11-19-2007, 01:45 PM
If my calculations are correct you nailed 1.03 G
Were I live 1G is 9.81 m/Sq.Sec, this values changes depending on how close you are to the equator so your value might differ slightly.
Formula: Velocity Squared / Brakingdistance X 2 = Deceleration
Jan
3140 w/driver is LIGHT. :)
I would have expected Penny to weigh more, is this really math for your car Steve? Stopping in 116 is fantastic on a street car! Rock on.
Steve1968LS2
11-19-2007, 04:26 PM
Nope, this is the Art Morrison 'Vette
I'm writing the feature for it right now. My car is 3180 without driver.. that Vette kicks ass!
Funny, I was just now reading the latest article in PHR on the 3G Vette and the details about the brake components. :)
I wondered if you might be referring to them! Small world.
sik68
11-20-2007, 11:22 AM
I agree w/ 1.04 G's average. And the weight of the vehicle is not used in calculating the deceleration.
What tires are on the vette?
Steve1968LS2
11-20-2007, 01:29 PM
I agree w/ 1.04 G's average. And the weight of the vehicle is not used in calculating the deceleration.
What tires are on the vette?
Michilin Pilot Sport Cup tires.. the problem with these tires is that we couldn't get them up to thier optimum temp. They are designed more for track use and the testing didn't stuff enough heat in them.
If they had been running an R-compound tire that required less heat (like NT01, R888, RA1) then I think they would have even stopped faster.
paul67
11-20-2007, 06:12 PM
Can you not hire a machine that does that,it sits on the pass seat , on our MOT test for braking in the old days thats what was you to test the brakes.
romar 02 SS
11-20-2007, 07:40 PM
27. Oh wait that might be wrong.Lets see v=... carry the 2...I'm lost...???... Yup 27.:seizure:
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