I rolled my car this past week and my physics teacher wants to find out at what speed i rolled it at. I need to find out the moment of inertia of the car... rolling from side to side... if any of you briliant people could help me out...

How'd you roll your car?

Wow. How did you roll it?

SuDZ

well we would probably use the forumla I=(mr^2)/2. find the mass of your car, the weight divided by 9.8. then get the radius of the axis of rotation which is headlights to tail lights, so measure ur roof from drivers winder to passenger window divide that by 2 to give you half and then sqaure it. times that by the mass and divide by two. i just used the disk moment of intertia so its gonna be a lil off and i dont feel like gettin my notes, but that will still give a close enuff number.

Remember, the mass of the car is not distributed evenly throughout its volume. You cant treat it like a cylinder of uniform density. This will require some complex integration to get right. Tell your teacher to shove it.

Or have him figure out his own dumb problem.

SuDZ

ur absolutely right, just figured it would give some numbers, but i didnt even think about that, o yea one more thing f@#$ ur teacher

Take the F+ on this problem.

If he wants to know the speed at which a maxima will roll, tell him to buy one and roll it himself

I still would like to know how one rolls a maxima.

inertia force = (car weight times acceleration) divided by G forces

Yes, but, that's not the moment of intertia which deals with rotation, or should I say deals with angular acceleration.

banked turn... took it to fast... rear end lost grip fish-tailed... counter steer... still sideways... hit the curb with front rear end comes around and hits the curb brings the car up into the air... when the rear lands the car flips and i roll once and land on the driver side door...

all of this was done with stock suspention and kuhmo supras or whatever they were called couple weeks old...

car status: max is totaled (pics next week maybee)... getting a wrx wagon

my status: cut by glass on my arm... then when the tow truck guy came i helped him turn the wheel and my pointer finger got cut...

You mean you weren't looking at your speedometer when you rolled it? Anyway, there can be a lot of other factors, like angle of the ground. I had a friend who rolled his Datsun 610 a few years ago at less than 5mph. He went around a turn too fast and went up on the embankment. The car was juuuust about at a dead stop ... and then ... it .... went ... Anyway, he smashed the roof and driver door pretty good. Worst part, he was dead broke and had just put a "For Sale" sign on the car. Ended up selling it to a junk yard cheap. It ran but looked like $h!t.

No formula will allow you to calculate with ANY accuracy the events you described, because you had so many compounding variables that induced the roll. (The rear wheel/tire left the road surface after hitting the curb, then came down & planted itself to initiate the roll).

It would be easier to come up w/ a number if the roll was caused simply by g-forces induced by tire adhesion on a flat asphalt surface.*

*(similar to the BMW video many people have seen of a 3-series at a Skip Barber racing clinic doing a horrendous multiple roll during an evasive maneuver drill - it's SICK )

Sorry, no link: if anyone has it, please post. It's impressive, let me just say that. Lastly, glad you're OK.