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Calculation of G Force

by ComposerCK
Tags: calculation, force
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ComposerCK
#1
Sep9-05, 02:09 AM
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.
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FredGarvin
#2
Sep9-05, 06:37 AM
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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

[tex]V^2 = {V_o}^2 + 2*a* \Delta X[/tex]

[tex](22.2 \frac{m}{sec})^2 = (69.4 \frac{m}{sec})^2 + 2 a (80 m)[/tex]

[tex]-4323.5 \frac{m^2}{sec^2} = 160a m[/tex]

[tex]a = -27.02 \frac{m}{sec^2}[/tex]

[tex]g's = \frac{a}{9.81 \frac{m}{sec^2}}[/tex]

[tex]g's = -2.75 [/tex]

I really hope this wasn't homework. If it was, you got a freebie.
ComposerCK
#3
Sep9-05, 07:30 PM
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 !!

huttojb
#4
Oct16-07, 09:38 AM
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
Shooting Star
#5
Oct16-07, 10:35 AM
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P: 1,979
Quote Quote by huttojb View Post
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.
huttojb
#6
Oct16-07, 10:41 AM
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)
huttojb
#7
Oct16-07, 10:42 AM
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
Shooting Star
#8
Oct16-07, 10:56 AM
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P: 1,979
Quote Quote by ComposerCK View Post
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.
Shooting Star
#9
Oct16-07, 03:10 PM
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Quote Quote by huttojb View Post
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.
rcgldr
#10
Oct16-07, 07:28 PM
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P: 7,134
Quote Quote by huttojb View Post
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:

http://www.motec.com/products/dash/adl2dash.htm
maddmax88
#11
Sep24-10, 11:06 AM
P: 1
I have a Physics problem that I cant Figure out:

An Aircraft goes from 0 MPH to 85 MPH during its take off run of 800 feet in 10 seconds. The aircrafts take-off weight is 2600 pounds and has 4 people aboard with 40 mounds of bags. What is the G-force experienced by the People on board?









'
Ranger Mike
#12
Sep24-10, 11:40 AM
Sci Advisor
PF Gold
P: 1,475
we did a lot of posts on this on MEch engineering forum and other forum here

Centripetal force- Car making a turn Jun6-10, 06:57 AM

race car suspension class Jul22-09, 11:03 AM

see post below in gen pyshics forumn..
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