Now that you have seen what kind of acceleration and top speed a car is
actually capable of, you may want to know what kind of braking your car is
actually capable of. Can your car really brake at 1-G? The actual value is
dependent on your tires, just as acceleration. To find the stopping distance,
you need to know your tires adhesive limit for the current situation. You can
then use the following formula to find the theoretical stopping distance:
d = v2
/ 2g*(adhesive limit)
So at 26.8-m/s, or 60-mph, you would get the following with 1-G rated
tires:
d = 26.82
/ 2(9.8)(1)
d = 718 / 19.6
d = 36.6-m
You would need 36.6-m, or 121-ft to stop at that speed. If it was
raining, and your adhesive limit was reduced to .7, it would take:
d = 26.82
/ 2(9.8)(.7)
d = 718 / 13.72
d = 52.3-m
In wet weather it took a lot more road to stop, 52.3-m or about 173-ft.
To take this a step further, let's see how long it would take to stop on snow
with an adhesive limit of .2:
d = 26.82 / 2(9.8)(.2)
d = 718 / 3.92
d = 183.2-m
This shows how dangerous it is to drive in snow. At 60-mph, it takes
183.2-m or 604-ft to stop. These values are usually even longer in real life.
this is because of brake fade. As you brake hard, they heat up due to the
friction. the heat causes the brake fluid to boil, and turn to a gas. The
braking force is then used to compress the gas rather than force the fluid to
compress the brakes. This effect varies from car to car, and is difficult to
calculate without extensive information.
The following table shows some important stopping distances and the time
to stop at the given speed. This values are for 1-G rated tires:
| Velocity (m/s) | Velocity (mph) | Time (s) | Distance (m) | Distance (ft) |
| 13.4 | 30 | 1.37 | 9.1 | 30.2 |
| 26.8 | 60 | 2.74 | 36.6 | 120.6 |
| 40.2 | 90 | 4.11 | 82.2 | 271.4 |
| 53.6 | 120 | 5.48 | 146.2 | 482.5 |
| 67.1 | 150 | 6.85 | 228.45 | 753.9 |
| 80.5 | 180 | 8.22 | 329.0 | 1085.6 |
| 93.9 | 210 | 9.60 | 447.8 | 1477.6 |
