# Statistics - A cars normal acceleration

1. Sep 11, 2007

### HalfLight

Hello, I'm looking for some sort of velocity time graph/table, which illustrates how a car accelerates in a range of 5 seconds or so. I'm trying to figure out at what point the car's acceleration will be higher than a runners acceleration. (It's only a matter of time before the car can overpower a runner, but during the first one or two seconds, a human has a higher acceleration because he does not need to get a grip with the ground first)

I've been searching the internet for a while now, but could not find anything. Could anyone point me in the right direction please?

2. Sep 11, 2007

### Danger

Welcome to PF, HalfLight.
All cars are different. For one that hooks up properly, the runner might have about 1/4 second or so of advantage. After that, it's game over.

3. Sep 11, 2007

### HalfLight

thanks for the response, but I am looking for concrete data. Does anyone know anyplace that could have something like that?

4. Sep 11, 2007

### Danger

This is still the proper place to ask; I'm just not the proper person to answer. My function is more of a greeter and a bestower of a rudimentary response. There are experts on board. In this instance, you might have to combine the inputs of the biomechanics/biology/sports medicine people (such as Adrenaline and Moonbear) with those of the automotively-inclined engineers such as Stingray, 'Stang and Brewnog. I'm not sure that any one person here has experience in both areas. As a general 'know-it-all' (in the best sense of that term), Astronuc might have a few thoughts about the subject.

5. Sep 11, 2007

### rcgldr

I assume you mean a track runner starting out of blocks and with spiked track shoes, otherwise the runner is traction limited as well as the car. I would assume a good runner could pull around 2g's of acceleration initially, which would quickly drop to less than 1 g after just 2 steps, and by 4 steps, very little acceleration.

The best "street" tires on pavement will pull about 1g, and for powerful sports cars, will pull this to about 35mph (Porsche turbo 911, 4 wheel drive, rear engine), or a bit less g force to 60mph (Corvette Z06) (about 3.4 seconds under good conditions). The high end motorcycles pull a bit over 1 g to around 80mph (Kawasaki ZX14, Suzuki Hayabusa).

A fuel dragster (rail or funny car) launches immediately with 4+ g's, well beyond what a runner could do.

6. Sep 11, 2007

### Loren Booda

http://www.kottke.org/06/05/horse-versus-human

In 1998, Ben Johnson (Olympic Gold medal sprinter banned due to steroids) raced against 2 horses and a car. He finished behind both horses and the actual lengths were different for each competitor...

"Johnson, who was stripped of his gold medal in the 100-meter dash in the 1988 Olympics, had to cover 80 meters (262 feet). The thoroughbred ran 120 meters (394 feet), the harness horse 100 meters (328 feet) and the stock car 140 meters (459 feet)." (NYT link

Also..."Johnson...who led for the first few steps but was overtaken quickly and finished several meters behind the winner." (CNN/SI)

7. Sep 11, 2007

### HalfLight

great thanks, now for one last question:

Is there any simple (or complex) formula to solve for the acceleration of the car by pluging in
friction, hp, rpm, etc?

8. Sep 11, 2007

### Staff: Mentor

It's the friction coefficient times g (assuming awd). Ie, a car with a friction coefficient of 0.5 will accelerate at half a g until the engine can no longer provide enough torque to keep that up (which usually happens when you shift to 2nd gear). For a car without enough power to spin its wheels, it's the thrust to weight ratio (which would be torque times the radius of the wheels) times g.