Using your common sense to solve a physics problem.

Before I start, or even think about this problem, which I have absolutly no experience in, and you can say this is for me, cause we all know it is. I don't have a problem with that.Why haven't you given me the mass of the car?
For me to figure it with common sense I might need this?
After all you gave me F=m*a. I don't know why you would give me this unless your just trying to throw me off.Before I start with the numbers, just glancing at it, I would take G and add the force of the incline to it, or possbly subtract it from the Uk. I will work the numbers, but I think I need the cars mass first. since F(grav)=m*g*sin(d) which would give me the force on the car plus the effect of the incline.Just so I can figure it out in my mind. Don't give me any more clues, I want to figure this out on my own.

I'm not sure what you mean by if you push at the end of the rod that 100% of the force goes into angular momentum.For me it would require less effort to push the end of the bar, but you would have to push it further. If you pushed from the middle of the bar, isn't 100% of the effort going into the angular momentum still? It would require more effort, but you would have to push it less distance?

I just read down. But I want to understand it further, and then explain it to you. I never said that common sense would replace knowledge. Given my common sense, and add some more knowledge, I would be smarter.My common sense would tell me however that the problem can be solved to a certain degree of accuracy. However it could never be totally accurate, as there aer many variables to consider, besides the ones you mentioned. but it would be close enough to say, yes he was speeding, or no he wasn't. This holds true for many things in science, and sometimes we tend to say yes or no, when we really don't know the answer. If you can understand that, then you will know where I'm coming from.But I really want to solve the problem, and show you my work, and describe how I came about my answer. Just so you won't think I am a bumbling idiot.You play chess? I would love to play you a game. Haven't played in a while, but I would be up for it.Hey, check this out, tell me what happened in this video, lol. Lets calculate the force required to stop that plane. I was the one flying the blue one, that I built myself. It flys again. 8ft wings 50cc 2 cylinder menthanol engine.
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Oh, ok, so its pivoting around O?
I got it now.It won't accelerate lineraly if the bar has flex in it.This message has been edited by riVeRraT, 09-23-2004 05:16 PM

I would hope that you could, but thats not my point.
If I had no training in any of this, which I don't or forgot what I did learn, I would be starting from scratch. That makes it harder.I don't know why you would get defensive, if your really not a jerk engineer. Tell me you haven't ever meet one?I've seen some things designed by engineers, and just laughed. When we (the mechanic) open our mouth to say it doesn't work, we used to get yelled at. So we were told to put it up the way it was designed. When it doesn't work, then it all has to come down again. This is where your tax dollars go. They hire $30,000 a year engineers, to tell $80,000 a year mechanics how to put something up.Besides all the paper work in the world, and formulas, you might still miss something, that I would see through my common sense, honed by 24years of mechanical hands-on experience. I pity the engineer that doesn't respect that.*edited to clarify something*I believe it is through the combined effort of both engineer and hands -on experience that something can go together right. I do not want to get rid of any engineer. But when this doesn't happen, it just sucks.This message has been edited by riVeRraT, 09-23-2004 05:23 PM

Ok so tell me, there is an aluminum I beam. It is attached at one end by a horizontal pin. The beam 12 feet long. The beam gets lifted from a point that is 8 feet from the pin. The end of the beam must carry a load of 3000lbs to a hieght of 6 feet from level.What thickness should the I-beam be, and what should the dimensions of the I-beam be, and what kind of aluminum should you use?Take as much time as you want.

I would like the mass of the car, even though you may not need it, I might so that it will lead me to the answer. There could be more than one way of figuring it out. I am not trained, so I will most likely be taking the long way.A variable could be the condition of the road on that day. Dry and wet are not the only conditions. Dew points and oil build up before a rain can affect traction conditions.The condition of the shocks and springs in the car can greatly affect how long it takes for a car to stop, as well as air pressure in the tires. Temperature of the tires at the time of lock-up can change a tires Uk. These are common sense things.

Me too. But the engineer is not the final word. This has been proven over and over again. Even when the data is correct, it is still subject to human error. If the engineer walks around with a head the size of yours, thats when the problems start.It's like I said, a combined effort is the best one. Many times the engineers can listen to the mechanics and learn something, or see something that couldn't be seen on paper.

Can I ask you a question? Why if I write this: You choose to over look that and only quote this: Isn't obvious where my attitude is at? Then you haven't meet enough engineers, or you are still honing your skills, and when you reach that eliteness or (l33tness) you will notice more jerk engineers. That is not to say that they aren't just as many jerk mechanics. refer to my 80% rule.80% of all people in all trades and professions aren't really that good at what they do, and most of that 80% borders on sucking. Try to find a good doctor, try to find a good car mechanic, go-ahead, I dare you. Probably because it has nothing to do with Uk.But I want it so I can see the whole problem. remember I am figuring this out the hard way most likely, because I have no training in it. But I will figure it out. I already have the basics as you can see. I just need to apply it in a formula. Knowing the mass of the car will help me understand Uk, better and gravity+sin(d)BTW I never took trig, I figured it out on my own, without a book, because I was a Sheet metal layout mechanic for 13 years. So with all the constant shaping of things from 2d to 3d, I needed to know about triangulation, which lead me to figure out sin and tan, except I never called it that. I can triangulate anything, I can cover you in metal, all I need is a 3 view picture of you, then your tin.

I think I have the formula, and I was doing that with M. I just want to see some things. I am a complex person, and I need to see the whole picture, which will lead me to the answer more quickly. Thanks for the help, but I will get it. I already understand whats going on, its just putting it in a formula.

Well it was 11 years ago. Thats NYC for ya.I have a few architects in my family and one civil engineer, I should have been one of them. I still might one day, officially.Unofficially, I own my own HVAC business, and have to engineer HVAC systems from blueprints. I caculate heat loads, and losses, and size the systems. Then I size the duct work base on a given pressure, and calculate CFM requirements.
I also design radiant heat systems, amd commercial refrigeration systems. So I deal with the coorilation between tempurature, and presure and the latent heat of evoporation on a daily bases.
I also trouble shoot all the electrics that control all this stuff.Then in my spare time I am an ameteur radio operator, and take pictures through my 8" telescope, and build and fly r/c planes.DEspite applying science in my life to all these things, I still found God

Yes I agree with all that.
But without having gone to college, I can look at what happened in the car crash, and I would be able to come up with all that on my own. It would take a long time, but I can do it.I am not so sure that even the most learned engineer, or scientist would be able to do that on his own, with out going to college.. That is my point.

It would less carrying capcity. I am talking about the carrying capcity of the completed project.The difference would be A-B=C
A being the original carrying capacity
B being the extra wieght of the extra nut and inch or 2 of rod involved.
C being the carrying capacity.The upper rod estends below the upper catwalk, and the rod connecting the upper cat, and lower cat is sticking up an inch or 2, thereby adding wieght to the catwalk, which decreases its carrying capacity.
Plus the extra nut (and washer, you do use washers don't you?).How'd I do teach?

Ok, using common sense skills only here is where I am at, and why I need the mass of the car to figure it out.For some of you, you were taught how to apply the coeffecient of kinetic friction to this. I didn't even know what that word meant. I knew what it was, I just didn't know what it was called. I also understand the difference between kinetic friction and static friction.I am going to ignore part 2 for the time being, and just figure out Part 1 using common sense.First I would need to figure out the force on the car by adding the skid with the grade of the hill.So I figure it like this. If at 0 degrees(or level) gravity has an effect of 9.8 m/s^2 Then 90 dgrees would increase it by 100%.The angle of which the car was sliding on was 13.875% increase on the effect of gravity and the Uk.So changing your formula around a little I came up with v=(2Uk*G*D)squared. Where D = the distance skidded. I converted the whole thing to miles, and feet, because Thats what I grew up with. V= the velocity of the car.So the effect of gravity is now 36.67m/s^2, the distance is 98.425 feet, and the Uk is .45So I get 56.992 MPH was the speed lost in the skid. Add that to the force of the impact between the 2 cars, and you'll get the total speed of the car.Crap, I hope this is right.

1 is not a good number to work with for common sense reasons.
Also pounds would be better. But I think I got it anyway.