bonnie
I play a nice person on twitter.
i turned out just fine. trust me.
Umm, who was talking about how you turned out? Tad defensive, dawg.
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i turned out just fine. trust me.
Umm, who was talking about how you turned out? Tad defensive, dawg.
So given that the visible damage is very consistent with a combined speed of ~80mph (or possibly lower considering what a tank the Model S is, while the Honda was 20 years old and comparatively fragile), is it your contention that the Honda was parked on the roadway?
Otherwise, the impact energies are subject to the laws of physics, in which case kinetic energy is calculated E=1/2mv^2.
Because the equation relies on the square of velocity, impact energies ramp up quickly with speed. Ignoring the units, 1/2*100*50^2 = 125,000 "whatevers" while increasing the velocity in the equation to 60 results in a total of 180,000 "whatevers" which is almost 50% more "whatevers" just moving the velocity from 50 to 60.
There is a reason that cars are not tested at combined impact velocities of ~140mph (which is what you would expect on a typical highway). The reason is that cars that are involved in a head on collision at that speed leave a smear of debris and gore as opposed to recognizable vehicles.
So given that the visible damage is very consistent with a combined speed of ~80mph (or possibly lower considering what a tank the Model S is, while the Honda was 20 years old and comparatively fragile), is it your contention that the Honda was parked on the roadway?
so you cannot compare "40mph into 40mph" with "80mph into parked car". The latter has twice the energy of the former because you add the squares, not square the sum.
Think about the physics a bit. Does the damage depend on the frame of reference? Ie does some someone traveling at 40 along side the honda, who perceives the honda as stationary and the tesla as going 80 (in this example) see a different outcome than someone watching from along side the road and sees them both going 40? Another way of phrasing this is what do you think Galilean invariance means?
I would like to take a moment to congratulate everyone for having the single nerdiest car club website on the net. Let the math continue....
Tell that to the wives and children of the two men who died. I think they'd kinda like to know if there was a culpable homicide there, alternatively the Tesla owner might like to be publicly exonerated if it wasn't his fault.
BTW, "ain't cool in no kinda way" is a double negative so either you mean it is cool or this was just provocative?
As was pointed out before, the issue is the change in velocity. Someone in the Honda frame of reference sees the Honda as stopped and the Tesla approaching at 80 mph. Then the collision occurs and the cars don't stop in that reference frame, rather they both move in the negative direction at 40 mph (assuming equal masses). So the energy of the Honda when from zero to 1/2 M * 40^2 and the energy of the Tesla went from 1/2 M * 80^2 (2 M * 40^2) to 1/2 M 40^2 and the net change in energy was M * 40^2.Think about the physics a bit. Does the damage depend on the frame of reference? Ie does some someone traveling at 40 along side the honda, who perceives the honda as stationary and the tesla as going 80 (in this example) see a different outcome than someone watching from along side the road and sees them both going 40? Another way of phrasing this is what do you think Galilean invariance means?
I would like to take a moment to congratulate everyone for having the single nerdiest car club website on the net. Let the math continue....
Apparently the usage was apropos; still shocked that some folks haven't heard of that particular word; guess having used it as a unix command line tool for decades it has become second nature for me.I'm sure the DIY EV group tops this bunch. And the Leaf group has a plethora of pocket protector types too. Tech cars, tech owners.
(proud I used the word plethora)
As was pointed out before, the issue is the change in velocity. Someone in the Honda frame of reference sees the Honda as stopped and the Tesla approaching at 80 mph. Then the collision occurs and the cars don't stop in that reference frame, rather they both move in the negative direction at 40 mph (assuming equal masses). So the energy of the Honda when from zero to 1/2 M * 40^2 and the energy of the Tesla went from 1/2 M * 80^2 (2 M * 40^2) to 1/2 M 40^2 and the net change in energy was M * 40^2.
Crashing into a parked car at 80 mph is very similar to two cars hitting each other head on going 40 mph.
However, that's not the same as hitting a brick wall at 80 mph even though the energy is the same.
The difference is there's no crumple zone in a brick wall so the average deceleration of the car during the crash into the brick wall is significantly higher.
Hitting a brick wall at 80 is similar in terms of energy to hitting a parked car at 80, true, but neither has the same energy as two cars hitting head on at 40+40. For "80 into brick wall" and "80 into parked car (assuming the car is anchored well enough not to move)" have 1/2m80^2 or 3200m energy. The head on 40+40 cars have 2 * 1/2m40^2 or 2 * 800m or 1600m or half the energy of the single car 80 example.
I find it helpful to consider the example of two identical cars, travelling at the same speed (say 40mph), hitting each other exactly head on. Both cars will stop dead, and the result will be the same as hitting a brick wall at the same 40mhp speed.