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Acceleration Parameters
Contents --
Acceleration due to Gravity |
Vehicle Acceleration and Braking |
General Equations
Acceleration due to Gravity
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Objects falling due to the force of gravity in a free fall increase in speed with time and distance. The exact acceleration rate varies slightly depending exactly where on earth the object is falling. The earth is not a perfect sphere and gravity varies slightly depending on location. By International definition 9.80665 meters per second per second (s2) is the gravitational acceleration constant, 1g = 9.80665 meters per second per second (m/s2) exactly.
Gravitational Constant (g)
9.80665 |
m/s2 |
32.17405 |
ft/s2 |
21.93685 |
mph/sec |
35.30394 |
kph /sec |
19.06260 |
knots/sec |
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Acceleration compared to free fall gravity acceleration g's is not a force. Force is mass multiplied by acceleration. The term "g" is a fixed acceleration baseline for comparison purposes.
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Vehicle Acceleration and Braking
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Maximum braking depends on vehicle weight and tire traction, width and diameter. Maximum vehicle acceleration depends on tires and horsepower. Top of the line production muscle cars can go from 0 to 60 mph in 5 seconds. Average acceleration is 60 mph per 5 seconds which equals 12 mph per second and equates to +0.55 g's.
0 to 60 mph in 5 seconds (+0.55 g's)
Time |
0 |
1 |
2 |
3 |
4 |
5 |
seconds |
Speed |
0 |
12 |
24 |
36 |
48 |
60 |
mph |
Distance |
0 |
9 |
35 |
79 |
141 |
220 |
feet |
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Adaptive Cruise Control systems, vehicle radar, automatically brake when approaching other vehicles. Maximum braking varies from -3 to -5 meters/sec2 (-7 to -11 mph/sec), or about -0.3 to -0.5 g's. Hard braking occurs around -0.55 g's
Deceleration g's
|
g's |
mph / sec |
Braking |
0.30 |
6.6 |
Safe |
0.35 |
7.7 |
Safe |
0.47 |
10.3 |
Average Driver Max |
0.62 |
13.6 |
Reasonably Skilled Driver Max |
0.66 |
14.3 |
Skilled Driver Max |
0.70 |
15.4 |
Vehicle Max |
1 |
21.9 |
Maximum Braking for select Vehicles
Productions years 1991 - 1995. Braking to a stop
measured on a dry flat surface starting at 60 mph.
Vehicle |
g's |
ft/s2 |
mph/s |
BMW M3 |
1.0 |
32.3 |
22.0 |
Toyota Celica GT |
0.94 |
30.2 |
20.6 |
Lincoln Continental |
0.92 |
29.6 |
20.2 |
Nissan Maxima |
0.85 |
27.3 |
18.6 |
Chevy Blazer |
0.76 |
24.5 |
16.7 |
Dodge Colt GL |
0.72 |
23.2 |
15.8 |
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Many safety experts use 15 ft/sec2 (0.47 g's) as the maximum deceleration that is safe for the average driver to maintain control, good to excellent tires, dry surface. A reasonably skilled driver can stop at 20 ft/sec2 (0.62 g's). Most production street vehicles have a maximum braking around 0.8 g's.
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Speed and Distance given Acceleration
v = vo + a t
d = vo t + 0.5 a t2
t = time
v = speed at time t
vo = speed when t = 0
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a = acceleration (-a for deceleration)
d = distance traveled at time t
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CopRadar.com
Police Radar Information Center
Acceleration Parameters
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