How many feet to brake from 65 mph to 35 mph?

Answer 1

Assuming constant rate of deceleration, then the formula is:

x = vavet

x = distance

vave = average velocity

t = time

vave = (v1 + v2)/2

v1 = 65 mph

v2 = 35 mph

vave = (65 mph + 35 mph)/2 = 50 mph

You are going to have to know another bit of information, which is the braking ability of the vehicle, in order to get t. For example, if the braking ability is -10mph/sec, then calculate that to reduce by 30 mph would take 3 seconds. I will use 3 seconds to continue the calculations.

x = 50mph X 3 sec X 5280 feet/mile / 60 sec/min / 60 min/hour = 220 feet

Remember that this is just an example. The actual distance depends upon the braking ability of your vehicle.