Very nice video from 2:10:
This maths might be useful to some on this thread:
Using Speed Difference and Distance
Convert the initial and final speeds to units that will be useful for calculating the acceleration (feet per second or meters per second). Also make sure the distance over which the speed change occurs is in a compatible unit (feet or meters).
Square the initial speed and the final speed.
Subtract the square of the final speed from the square of the initial speed.
Divide by two times the distance. This is the average deceleration rate.
Calculate, as an example, the deceleration required to stop a car in 140 feet if it is traveling 60 mph.
Convert 60 mph to 88 feet per second. Because the ending speed equals zero, the difference is this result squared: 7,744 feet squared per second squared. The deceleration rate is:
77442×140=27.66 feet per second per second 7744 / {2 x 140}=27.66 { feet per second per second} =27.66 feet per second per secondDeceleration in Gravity Units (G’s)
Calculate the deceleration rate using one of the two methods described above.
Divide the deceleration by the standard gravitational acceleration. In U.S. units, this is approximately 32 feet per second per second. For metric units the standard gravitational acceleration is 9.8 meters per second per second. The result gives the average number of G’s applied to achieve the deceleration.
Enhance understanding by considering an example: Find the G force required to stop the car in the previous example.
The calculated deceleration equaled 27.66 feet per second per second. The deceleration is equivalent to:
27.6632=0.86 G’s {27.66/32}