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Physics of a Car-Cyclist Collision

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Road Cycling It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle. -- Ernest Hemingway

Physics of a Car-Cyclist Collision

Old 04-21-10, 02:23 PM
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SalsaPodio
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Physics of a Car-Cyclist Collision

This guys physics knowledge is unbelievable

The comments section is pretty hilarious as well.

http://www.iowastatedaily.com/articl...89101.txt#main
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Old 04-21-10, 02:28 PM
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Are there consequences to bicyclists other than the occasional death by splat? Not usually.
The guy has such a way with words.
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Old 04-21-10, 02:29 PM
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This guys a Senior studying Econ? Wow! Amazing the thought process of someone who is supposedly well educated.
I wonder if he'd like a little cheese with his whine?
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Old 04-21-10, 02:35 PM
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Originally Posted by HIPCHIP View Post
This guys a Senior studying Econ?
Maybe the letter should be titled "Economists should stay out of physics discussions."
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Old 04-21-10, 02:35 PM
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*sigh*
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Old 04-21-10, 02:38 PM
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"That means that you will be exerted to nearly 1.3g's."

Hope his grasp on economics is better than his grasp on physics.
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Old 04-21-10, 02:41 PM
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Let's play:


Mass of truck = 6,400 pounds = 2,800 kg
fine

Velocity of truck = 30 mph = 13 m/s
ok. sorta. not really. try google

Mass of man and bike = 220 pounds = 100 kg
you just picked that to make the numbers round. kinda like this "bicyclist"

Velocity of man and bike = 0 mph = 0 m/s
He's just standing there? Maybe you mean in the direction perpendicular to the velocity of the truck. fine.

Kinetic Energy = (1/2)*m*(v^2) and energy in = energy out
Energy isn't destroyed, but don't kid yourself that kinetic energy is conserved

Momentum = m*v and momentum in = momentum out
ok, this is what you REALLY mean. fine.

Final velocity of the combined masses of the truck, bike and bicyclist = 12.5 m/s = 28 mph
Nope. 29mph. good try

This means that you will be exerted to nearly 1.3 gs.
No it doesn't. you don't know anything about the mechanics of this collision. exerted isn't even remotely the right word.

The change in kinetic energy of the bike and bicyclist = 7200 kg*m/s^2 = 7.2 kJ
kg*m/s^2 = energy. are you high?

Assuming the collision lasts one second, the bike and bicyclist will feel 7.2 kW
ECT (as my wife writes on her grading, this means error carried through). This is right, but unfortunately you need to assume a bunch of stuff and isn't really right anyway.

Man, I miss the midwest.
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Old 04-21-10, 02:42 PM
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Originally Posted by richardmasoner View Post
Maybe the letter should be titled "Economists should stay out of physics discussions."
+1
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Old 04-21-10, 02:48 PM
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Gotta love the Tom's Dad response.
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Old 04-21-10, 02:52 PM
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nuts
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Old 04-21-10, 03:04 PM
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despite his alleged lack of physics knowledge, i do agree strongly with:

You have seen them weave through traffic, ignore stop signs and switch seamlessly from sidewalk to roadway in the blink of an eye.

This is a blatant lack of respect for other people on the road
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Old 04-21-10, 03:32 PM
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Originally Posted by blamire View Post
You have seen them weave through traffic, ignore stop signs and switch seamlessly from sidewalk to roadway in the blink of an eye.

This is a blatant lack of respect for other people on the road
If a cyclist filtering forward past stopped traffic is blatantly disrespectful, what is the motorist who passes the cyclist in the lane? If the motorist is not 'blatantly disrespectful,' why are these two situations different?

Richard
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Old 04-21-10, 03:41 PM
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Originally Posted by richardmasoner View Post
If a cyclist filtering forward past stopped traffic is blatantly disrespectful, what is the motorist who passes the cyclist in the lane? If the motorist is not 'blatantly disrespectful,' why are these two situations different?

Richard
They're different when the car is actually going to maintain a faster pace and continue on well ahead of the cyclist. It's just forcing him to pass a second time. I don't really get filtering. It seems kind of pointless. Maybe it's the traffic I ride in though.
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Old 04-21-10, 03:47 PM
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After reading the linked page, it sounds to me like this young man has been watching to much Glen Beck....(or worse Pat Robinson).....his tone is from the same school of commentary ....you know,....."the lacking any real knowledge about what I am talking about, but I will whine and complain about anyone different than me" .. school of ranting.

To me, the bigger issue/worry is that some editor and/or faculty advisor at the Iowa State school paper actually let it this moron's ranting be published........
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Old 04-21-10, 04:26 PM
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I like your rights and privileges should be proportional to the amount of taxes you pay argument. I would come out WAAAAY better in that world.
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Old 04-21-10, 04:37 PM
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Originally Posted by Phantoj View Post
"That means that you will be exerted to nearly 1.3g's."

Hope his grasp on economics is better than his grasp on physics.
Hope it's better than his grasp of English, too.
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Old 04-21-10, 04:40 PM
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This kid isn't intelligent at all, his little essay was a fail.
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Old 04-21-10, 04:41 PM
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There are some really bitter people in this world.
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Old 04-21-10, 04:47 PM
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I'd gladly pay $55 a year (what my license plates cost a year) to ride my bicycle in an actual bike lane, between the right lane and the shoulder, guaranteed anywhere that I want to ride, with at least minimal standards of upkeep. That means I never have to plan my routes to avoid busy streets without shoulders.

I'm sure this guy does drive a fossil fuel consuming pickup truck. Complete with raised suspension, mud tires, glass pack muffler, and a confederate flag in the back window.
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Old 04-21-10, 04:53 PM
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I love how he goes from a Velocity to an acceleration. (I'm assuming he thinks that g means 9.8 m/s)

Remember, these are the people the f*ed up the world's economy.
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Old 04-21-10, 05:28 PM
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Originally Posted by crhilton View Post
It's just forcing him to pass a second time.
And so he passes a second time. And the big deal is ... ? It's just traffic, after all.

If a motorist will get in my way at the next intersection (and they frequently do), I don't consider it rude or "disrespectful" (good Lord) for them to get in my way. If there's room, I'll filter. If not, I hang back, or maybe find a nice SUV to draft behind.

Here's a photo I shot of myself after filtering through about a mile of stopped traffic (long light, evening commute). The motorists will pass me after the light turns green. Do you really expect a cyclist to queue up at the end of that line?



Last edited by richardmasoner; 04-21-10 at 05:29 PM. Reason: typo fix
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Old 04-21-10, 05:52 PM
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One more thing, bicyclists may pay state and federal taxes just like everyone else but that does not give the right for them to be on the roads. A person who is blind will pay these same taxes do they have the right to be in vehicles on the road? No, bicyclist should have to have their vehicle(s) of choice registered, licenses, and pay the taxes related to have a vehicle registered and licensed
Apparently blind people aren't allowed to ride in cars.
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Old 04-21-10, 06:21 PM
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I think the morons should be told that the majority of the funds that pays for roads comes from the general fund not from gas taxes or lic. plate fees. And that cyclist have held the right to ride on the road since before there were cars.
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Old 04-21-10, 06:33 PM
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The best part is the assumption that the energy of the collision will be applied over an entire 1 second. Which for a vehicle going 30 mph would occur over a distance of 44 feet. When the reality is that in a square hit the energy transfer would occur over a distance of more like 1-2 feet. His estimates of impact energy are easily a full magnitude off.
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Old 04-21-10, 07:07 PM
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Bike Snob responds...

It's really this blockheaded inability to recognize the humanity of others that is the root of almost all animosity out there on the roads.
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