Brake Question

[dyna]

I forget, but somewhere I was reading this but I don't know if it's true,
can a car brake from 70mph-0 in 14 feet.
Thanks,
Shane

[Alastor187]

Originally Posted by dyna

I forget, but somewhere I was reading this but I don't know if it's true,
can a car brake from 70mph-0 in 14 feet.
Thanks,
Shane

On the back of stamp book I calculate:

70mph = 102.667ft/s
0mph = 0 ft/s

Vf = Vo + a*t
0ft/s = 102.667ft/s + a*t
a*t = -102.667ft/s

d = Vo*t + 0.5*a*t^2
14ft = 102.667ft/s*t + 0.5*(-102.667)*t
t=0.273s

a = -102.667ft/s / t
a = -102.667ft/s / 0.273s
a = 433.194ft/s^2 (average)

g = a / 32.2 ft/s^2
g = 433.194ft/s^2 / 32.2 ft/s^2
g = 13.453g (average)

--

A high performance tire on a high performance street car may be able to approach 1g of acceleration but nothing close to 13.5g. Even F1 does not exceed more than 5gs or so in any direction, and that is just a peak acceleration.

Maybe you are taking about just one car specially designed to do it? I am sure it could be done using special tires, brakes, aerodynamics, parachutes, rockets, glue on the road, etc.

Although the best bet would be a ridged body like a concrete wall ;-)