# Calculation of G Force

by ComposerCK
Tags: calculation, force
 P: 2 Hi, I'm hoping someone can provide me with a formula to calculate the amount of G Force experienced when decelerating, based on this information : A 250cc International Superkart is travelling at 250km/h and is approaching a tight corner than can be taken at a maximum of 80km/h. The driver leaves the braking to the last possible moment, and decelerates from 250km/h to 80km/h in a distance of 80m (whilst in a straight line). How many G's has the Superkart and driver experienced ? Thanks, Chris.
 Sci Advisor P: 5,095 It's pretty straight forward if you neglect friction and wind resistance, etc... Note: 250 km/hr = 69.4 m/sec and 80 km/hr = 22.2 m/s $$V^2 = {V_o}^2 + 2*a* \Delta X$$ $$(22.2 \frac{m}{sec})^2 = (69.4 \frac{m}{sec})^2 + 2 a (80 m)$$ $$-4323.5 \frac{m^2}{sec^2} = 160a m$$ $$a = -27.02 \frac{m}{sec^2}$$ $$g's = \frac{a}{9.81 \frac{m}{sec^2}}$$ $$g's = -2.75$$ I really hope this wasn't homework. If it was, you got a freebie.
 P: 2 Thanks for that !! No, it wasn't homework of any sort ....... unfortunately I'm not studying Physics at all. I must look into that formula so that I understand the parameters used and their relationship. The speed into metres per second was obvious anyway, but I probably lack the basics to understand and agree with the rest of it. I can see that 4816.3 - 492.84 = 4323.52. I wouldn't have thought friction and wind resistance would have been a factor in G force ....... ? -2.75 G's ....... my guess before reading the answer was between 2 to 2.5 G's, based on what I've heard for a Formula One car ........ Once again, thanks for taking the time to reply !!
 P: 3 Calculation of G Force Hello. I'm new on this forum so hello to everyone. I'm attempting to monitor the G Force in a vehicle whiles it's driving, does anyone have any ideas? All I have is the speed of the vehicle, would this be enough to measure the G Force? jason
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P: 1,982
 Quote by huttojb All I have is the speed of the vehicle, would this be enough to measure the G Force? jason
No. If the vehicle is moving in a st line with constant speed, there is no g force due to motion of the vehicle.

You have to know the acceleration. If you are moving with a constant speed on a circular track, then you have to know the radius of the track and the speed.
 P: 3 But obviously the vehicle needs to go from 0mph to (say) 90mph, Obviously any variation in speed will result in G Force?? Is this correct? Let's say for arguement sake, it's in s straight line? How would I work out a running G Force? i.e. Like the one on F1 (ITV)
 P: 3 Lets expand on that. If I made a trip from A to B, I would want to know the maximum amount of G Force I went through during this trip? Can you Help. Ta
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P: 1,982
 Quote by ComposerCK A 250cc International Superkart is travelling at 250km/h and is approaching a tight corner than can be taken at a maximum of 80km/h. The driver leaves the braking to the last possible moment, and decelerates from 250km/h to 80km/h in a distance of 80m (whilst in a straight line). How many G's has the Superkart and driver experienced ? Thanks, Chris.
The actual g force experienced by the driver would be the magnitude of the vector sum of 'a' backward and g downward, which will be equal to sqrt(a^2+g^2)=2.93g. This g force is at an angle tan-inverse(a/g) to the vertical.
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P: 1,982
 Quote by huttojb Lets expand on that. If I made a trip from A to B, I would want to know the maximum amount of G Force I went through during this trip? Can you Help. Ta
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Hi Huttojb,

You need some more parameters to find the accn or the g force. If you know the time 't', and accn is constant and the motion is in a st line, then the accn 'a' is (90-0)/t mph/h.

If you know the dist, then too you can find the accn if it is constant.

In practice, the accn is generally not constant. So you would need a detailed dist-time graph; or hang a spring balance in the car to see the effective g force. (Note that the reading on the balance would include the g field of the earth.) The maximum accn would perhaps be when you start and reach a high speed in a few seconds. Or when you slow down by stepping on the brakes very hard.
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P: 7,047
 Quote by huttojb I'm attempting to monitor the G Force in a vehicle whiles it's driving, does anyone have any ideas?
Do a web search for "accelerometer car", you'll find a few companies that sell these, or do a search for "data acquisition car" for high end systems such as this Motec: