| Author | Message | ||
     Court |
That's inaccurate. | ||
| Court |
No one, myself included, did such a thing. One of the maladies of discussing on a motorcycle internet chat area is that folks with varying opinions tend to **think** the other person called them stupid. I deal with stupid people day in and day out and know exactly what they look like. I find them on the streets, at work and in class at school. They tend to be represented uniformly in society from the ranks of the homeless to grad students in SEAS (School of Engineering and Applied Sciences) here at Columbia. And . . as those who know me will affirm. . . If I were calling you stupid, there would be no doubt about what I had said. I'm generally quite clear. It comes with old age. | ||
| Court |
By the way . . . try this one. Imagine . . .for a moment that you are a human Stress-o-meter and you live in the middle of a rope. Tell me the difference between two people pulling on each end of a rope, and one person pulling on a rope tied to a tree.  | ||
| Darthane |
Let me guess. . . if two cars collide head on, each going 100MPH, you'd say that was the same as a single car hitting a wall at 200MPH? If you weren't implying that I'm ignorant (a better choice of word on my own part than what was used) of physics, then you you probably should have phrased it differently.  | ||
| Court |
Here. .. read this, I've got a 1:00PM class. Back in a bit. | ||
| Rpm4x4 |
Let me guess. . . if two cars collide head on, each going 100MPH, you'd say that was the same as a single car hitting a wall at 200MPH? I don't think there is any worry of a smart going 100mph! | ||
| Spiderman |
He also said somethin about yo mama! | ||
| Darthane |
Court, I'm beginning to think you're not even reading what I wrote, so I'll just post this quote from the link you provided and call it a day. You can't discuss when one side isn't listening. c) automobile going 50 mph encounters a brick wall of infinite mass traveling 50mph in the opposite direction. In this case, the automobile has to decelerate from 50 mph forward to 50 mph backward in a very short period of time (since the wall doesn't give at all). This is the equivalent of hitting an unmoving brick wall at 100 mph. Twice the deceleration, twice the damage as the above two situations. Situations like this occur when a passenger car crosses the middle line of a roadway and encounters a tractor-trailer going the other way. Since the truck is of very large mass compared to the car, the car suffers most of the deceleration and takes most of the damage, and the collision is considerably worse (for the car) than hitting an equivalent-weight car or a stationary object. For the truck, the collision is considerably better than hitting an equivalent-weight truck or stationary object. | ||
| Prof_stack |
Concerning the rope question: We did an experiment in class where two people of very different size/strength each held a bathroom scale and pressed it against the other scale as hard as they could but so that no one moved. The scales were examined and, to the shock of the big guy who figured he was more forceful, both read exactly the same. | ||
| Darthane |
so that no one moved. That's the important part of the equation. There is no acceleration, both sides of the equation are balanced. The same is true of Court's original post on the matter. His cars have equal mass and are traveling at the same speed, and hit head-on - thus they decelerate at the exact same rate. This really doesn't happen anywhere except in a controlled experiment. In your case, the larger, stronger person likely could exert more force, but you placed a limiting factor on him - the scales were not allowed to move, thus he was limited to exerting the same amount of force that his opponent used. Cars involved in accidents, in case it slipped anyone's perception, do not care if you told them both to stop at the exact same point irrespective of their mass, unlike the two people in your experiment. They will obey the laws of physics each and every time, and that means that the car with more mass will decelerate more slowly. When a Smart car hits a Suburban head on and both are traveling the same speed, the equation is not balanced by a long shot. (Message edited by darthane on July 30, 2008) | ||
| Darthane |
Getting back to the original gist of the post - that little convertible Smart is pretty sweet looking. The ForTwos that they sell here in the States have the cute puppy dog appeal going for them, that thing actually LOOKS badass. I kinda think it would be along the lines of my Blast, though. It looks 'right' until there's a person in/on it to provide some scale, and then you realize just how tiny the thing really is! | ||
| Xl1200r |
Imagine . . .for a moment that you are a human Stress-o-meter and you live in the middle of a rope. Tell me the difference between two people pulling on each end of a rope, and one person pulling on a rope tied to a tree. Court, your example holds water, until you change to something like: Imagine . . .for a moment that you are a human Stress-o-meter and you live in the middle of a rope. Tell me the difference between two people pulling on each end of a rope, one being an infant (the Smart Car) and the other being professional body builder (the Chevy Suburban you jan ran into), and one person pulling on a rope tied to a tree. I think you can see the difference. There's no doubt that when hitting a sationary object, a smaller car can be safer with a smaller crumple zone because it has less energy to absorb at a given speed than a larger vehicle does at the same speed. But when the little vehicle hit the larger vehicle in something resembling a head-on collision, the little guy gets the raw end of a deal. I have no problem admitting that you are LOADS smarter than I am when it comes to this kind of stuff, but I don't think many people need a degree to know that if a cannon ball and golf ball are thrown at one another, the cannon ball probably isn't going to care all that much, lol. | ||
| Thumper74 |
Uhh... What are the mass and velocities of the cannon ball and golf ball? | ||
| Scott_in_nh |
That's inaccurate. Uhmm, no it isn't.... If a baseball is thrown at 100 mph and it strikes a bat going 100 mph the impact might send the ball over the wall. If a baseball is thrown at 100 mph and strikes a bat that is stationary your get a bunt. The ball was decelerated to zero in both cases, but with greater G force when the bat was swung. Let's say that the ball will crush 1/4" on the impact side while decelerating from 100 to 0. Against a stationary wall it travels the same 1/4" while decelerating. Against a non-deflecting surface of a larger mass traveling 100mph in the opposite direction the ball still crushes 1/4" but it only traveled 1/8" to do so and it happened in half the time, doubling the G force (the non-deflecting surface traveled the other 1/8" in the opposite direction during the same time period). Once the ball is at zero the overwhelming force from the greater mass of bat is imparted into the ball causing it to accelerate in the opposite direction (Smart Car bouncing off of SUV many feet and rolling over). Once the ball is at zero against the immobile bat, the compression of the ball rebounds sending the ball into the infield (Smart Car bouncing backward a few feet off of stationary wall). PS. I have no trouble admitting you are smarter than me too, but I think I am right on this one.... (Message edited by scott_in_nh on July 30, 2008) | ||
| Greenlantern |
Seems odd to have people arguing about how safe the smart car is or is not on a motorcycle forum... Oh that's because we wear gear, so..........uh... we are.....uh...HEY LOOK! QUEEN ELIZABETH IN A THONG  | ||
| Xl1200r |
Uhh... What are the mass and velocities of the cannon ball and golf ball? Sorry, forgot the specifics. Assume both are traveling at the same rate, the cannon ball weighs 10 lbs and the golf ball weighs 1.62 oz (as dictated by the United States Golf Association). | ||
| Darthane |
Exactly, Thumper. You CAN get the equation to balance out, resulting in equal deceleration, but that golf ball is going to have to be moving a HELLUVA lot faster than the cannonball to make up for the differences in mass. If you change one variable, the other one has to change as well. Seriously, do any of you really have any doubt about this? How many times have you seen a passenger vehicle, even a large SUV, completely destroyed in a collision with a semi or train or something similar? If the car had hit a tree, it would have decelerated to 0 and been done with it. The tree simply resisted the force exerted on it with an equal and opposite reaction. The same thing would have resulted had it hit a car of the same mass moving in the opposite direction. I'm not denying that, in fact, I've agreed with it several times. The problem in the case of the semi or train or even just a larger car is that they have a lot more force to exert, so they not only decelerate the vehicle to 0, but then accelerate it in some other direction, resulting in more damage - or at least the potential for it. | ||
| Thumper74 |
My understanding that all things being equal... a 1,400 pounds Smart car travelling 60mph will do the same amount of damage as a 2,800 pound vehicle travelling 30mph. The golf ball made out of the same material traveling at a much higher velocity would have the same kinetic energy as a the bowling ball... right? | ||
| Josh_ |
What would the contact patch be for the Smart Car? | ||
| Court |
I learned a great deal about the basic F-MV2 the day I needed to move a Burlington Northern box car in Stillwell, KS. I was by myself, the car was about 50 yards from where I had to unload it. There wasn't a soul around for 25 miles. After about 25 cycles of climbing into the door, picking up a Lapp insulator string, carrying it to the door, setting it down, jumping out, lifting it over my head and carrying to the pile across the yard . . . I was struck by a "if the car were only closer to the pile" vision. I had a K20 Chevrolet power wagon and a 30' proof 3/8" log chain. What could be easier? I pulled the pickup along side the box car, got out, attached the chain to the metal steps, jumped in, slipped the 4WD in low range and gently feather the clutch until I got the car in motion. About this time Professor Larry Peck's lecture on momentum began to play in my mind in perfect harmony with the basic Newtonian premise about "an object in motion tends to stay . . . " It was that whole tends to stay part that began to haunt me as I reflected on the fact that it was pretty well down hill for the next 42 miles to Kansas City. These are the types of lessons that stick with you forever and provide wonderful "real world picturization" examples when sitting in a final at school. Fun with physics. | ||
| Blake |
The insect hitting the windshield might offer a telling perspective concerning the effects of relative mass in a head-on collision. | ||
| Darthane |
...particularly big, fat june bugs to the faceshield.  | ||
| Court |
Ohmygosh . . . . . Blake found our physics discussion. . . everybody RUN and I take back everything I said.  We are SO busted! | ||
| Doon |
Darthane: ...particularly big, fat june bugs to the faceshield. Which is why I wear a full face helmet (and my brother does too now). Take one of those in the middle of a cornfield at 60+ and see how it feels -Patrick | ||
| Darthane |
My lessons concerning the necessity of full-faced helmets include gravel trucks and a pigeon...and, yes, june bugs. ...none of which are pleasant at freeway speeds! LOL | ||
| Doon |
Well living in farm country you can add hay wagon and/or Sh*tspreader to your list The latter not being pleasant at any speed... | ||
| Reepicheep |
Thats where the hint is... and I think that statement is wrong. The little car will experience a more radical deceleration (which is what you care about), but both vehicles will experience the same "force". Each bumper pushes on the other, one can't get a bigger push then the other. But I think both sides have some truth here. Decelerations will be different, but forces have to be equal. Object A has to impart Force B on object C, and object C will be imparting an equal force on object A. Depending on the relative masses, the resulting deceleration associated with these forces will be radically different though. And deceleration hurts. And there is the whole energy is Mass times Velocity squared. I would much rather get hit by a 1000 pound object moving 1 mph, then a 1 pound object moving 1000 mph. Think chunky salsa. Physics... its always obvious... about the fourth time I think it through  (Message edited by reepicheep on July 30, 2008) | ||
| Darthane |
His wording should probably be changed a bit, but I was quoting verbatim. The statement should read something along the lines of: 'the cars suffers quicker deceleration', not 'more of the deceleration'. The results are the important part, here. Semi = 1, car = 0. | ||
| Birdy |
The F-4 and the wall. http://www.youtube.com/watch?v=4q35xHzjxB0&feature =related | ||
| Xl1200r |
The statement should read something along the lines of: 'the cars suffers quicker deceleration', not 'more of the deceleration'. I don't think there's anything wrong with the statement. If a car going 50mph goes head first into a train going 50mph, gues what happens. The car decellerates from 50mph to 0mph, then accellerates in the opposite direction from 0mph to probably about 49mph. The train keeps on chugging, probalby loosing less than 1 mph in speed. If the train decellerates by 1 mph, and the car decellerates by 99mph (50 to zero + 0 to 49), then the train decellerated less than the car. "1 is less than 3,000." |
