Today's physics lesson: An object in motion will stay in motion

[rolanni]

Careful auditors of this journal will recall that yesterday in these parts, it snowed. After it snowed, it sleeted (slet?) for a while, then rained. It is currently snowing again, quite prettily.

This means that, despite the best efforts of the City of Waterville and the college grounds crew, the streets are covered in -- anybody? Yes, you in the back -- Yes, thank you, very good.

The streets are covered in SNOW. Snow, for those of you who live in the Warm Lands, is slick.

So, I'm driving up the hill, keeping well back from the car in front of me, and thinking that the little green Subaru is champion, when what should happen but that a Citizen of the Campus, without even looking, steps into the street, dangerously close to the lead vehicle. The driver slams on the brakes, not wishing to bag a student out of season -- and the car slides.

The kid -- is a lucky, lucky kid. The driver probably aged twenty years. The kid, alas, does not know his luck; as far as I could see, he never turned his punkin' haid.

Now, yes. The Rule on campus is that walkers trump vehicular traffic; we in cars must stop to let those on foot cross the street. But, honestly, it might not be a bad idea to, yanno, consider conditions, and cut the poor, lumbering automobiles some slack.

Comments

[jhetley.livejournal.com]

Think that Kid will live long enough to breed? Evolutionary pressure . . .

Slippery over here, too. Just finished first round of cleanup, with an inch or so of slush under the snow. But, like they say in the Marden's Surplus and Salvage ad, "New deliveries daily!"

[kinzel.livejournal.com]

We had more snow at the house, which obligingly finished up about the time the plowguy stopped by. Alas, a slip on the steps this morning revealed a problem with the side rails, so played rough carpenter -- sliding off the side of the stairs is a good way to get hurt in the ice and snow.

In theory, we're almost clear except for some snow showers until Saturday night.

[ariaflame.livejournal.com]

Do you get black ice? That's even nastier from what I remember my parents saying.

[keristor.livejournal.com]

We get black ice in the UK. Possibly more often than we get real snow, in the southern parts, since our daytime temperatures are often above melting point and then the wet roads freeze overnight.

[(Anonymous)]

Yeah, when "the universe revolves around me" meets the laws of physics, the laws of physics win.

Last winter, after a snow, I needed to cross a 6-lane road. Normally it's a very busy street, but next to nobody was on it in the weather. The light changed and I got my walk signal. I looked up at the only car coming, judged it as being far enough back and moving slowly enough that it planned to stop at the red light, and started across the street. Car began honking frantically. I stopped, and watched as the car passed at a walking pace in front of me and slid slowly and majestically on through the intersection. Darn, it was slick out that morning.

[kinzel.livejournal.com]

And you both showed excellent reactions.

[fridayflute.livejournal.com]

Ah, yes. As a kid learning to sail I was thrilled by the idea that I had the right of way over big, noisy powerboats...until my father reminded me of the saying "Here lies John O'Day, who died defending his right of way." Moral of the story - if its bigger let it go first, momentum trumps all.

I spent part of a Christmas holiday in Reykyavik, Iceland many moons ago, and remember being awed by the way drivers timed their braking so that the ensuing slow skid ended just at the intersection. Given their climate, I suppose they get plenty of practice!

not wishing to bag a student out of season --

[bookmobiler.livejournal.com]

What is the season on students? And what is the bag limit?

If that student was majoring in physics I don't like his chances of graduating.

An old time New Englander once told me that the ideal method of driving in winter conditions was never to touch the brakes.

[jerusha.livejournal.com]

General Rule: When the Laws of the Land are in conflict with the Laws of Physics, Physics wins. The fact that the driver is legally at fault for the collision is likely to be of little comfort to the grease spot that once was a pedestrian...

(Corollary, addressed to many drivers I see on my morning commute: 4WD helps greatly with Go. It does nothing for Stop. Forget this at your peril. Or at peril of wiser drivers pointing and laughing as you repine in the ditch.)

Also: there's a period when students are in season? O Teacher, tell me more!

[torrilin.livejournal.com]

It also helps if the Laws of the Land are not in conflict with Geography. Or, thou shalt not put a stop sign at the BOTTOM of a hill. Top yes, bottom no.

If you detect that the Laws of the Land are habitually in conflict with the Laws of Nature, be aware and venture forth at your peril.

[keristor.livejournal.com]

4WD works a lot better to stop you if (a) you have a stick shift or a lockable low gear so you can use engine braking (auto just puts the thing into high gear usually), (b) you know how to use it and (c) you don't use the brakes (they just lock up the wheels and you slide). Unfortunately few drivers seem to have learned any of those (even in Germany where they get snowy winters a lot).

Also, in respect of physics -- nature may abhor a straight line most of the time, but she really likes them when you try to turn a corner on ice. It generally doesn't matter much which way the car is pointing, the center of mass just keeps straight on. (Except for my first car, which had incredible grip. I coudn't skid it at all even on sheet ice unless I trod on the clutch and hit the brakes hard, and it actively enjoyed going up a 1 in 7 snow-covered road where some had been shovelled and then frozen again. A 1971 Austin 1300GT...)

[jhetley.livejournal.com]

Antilock braking systems are a Good Thing.

[jerusha.livejournal.com]

Oh, yes. However, in my admittedly-conservative style of driving, if the ABS engages, someone is Doin It Rong. In this case, it was the pedestrian. But if I'm driving fast enough or braking hard enough that the ABS engages for anything other than an emergency like that, I'm driving badly and should back off some.

[jhetley.livejournal.com]

I think that the last time I heard our ABS chatter at me, it was when I discovered that a recently-painted crosswalk just before a traffic light was a black-ice emulator. Stopped in plenty of time, anyway, but . . .

Prop 8 didn't go far enough.

[(Anonymous)]

Sorry about the off topic post but I saw this and couldn't help but chuckle about it. Thought maybe some of the regulars here would also.

http://www.cnn.com/video/#/video/bestoftv/2009/12/04/tsr.ca.movement.to.ban.divorce.cnn

Nathan

Pedestrirans have right of way in a crosswalk ...

[elgordo303.livejournal.com]

it's a state law here in frigid Minnesota. I've never thought it to be a particularly good idea to arm someone, with an average level lack of common sense, with the idea that the rule of law trumps the laws of physics. Dying defending right is an honorable death ... dying defending right of way ... not so much.

[trolleypup.livejournal.com]

The way I've always heard it... As a pedestrian, you have the right of way, which, if you insist on it, will make you dead right.

[nephir.livejournal.com]

Yeah.... what you said. Life in the PacNW is frozen right now, but with no local snows or rain for which we are truly thankful.

Good for you

[(Anonymous)]

I also want to comment positively on something I don't think others mentioned. GOOD FOR YOU for "keeping well back from the car in front of me" It has been my horrified observation of drivers down here in sometimes snowy and icy Northern Virginia that their persistent habit of tailgating can very quickly become the demonstration of the aforementioned inexorable Laws of Physics, that the object in motion, on an slick street, remains in motion until it collides crunchingly and blasphemously with the object in the lane in front of it!

Anne

Fools and Angels

[(Anonymous)]

Somebody's guardian angel is doing overtime.

A couple of winters ago, I set out to pick up a friend from BWI,
traveling slow and steady. As I approached the first big
intersection (with another car coming from the opposite direction,
also slow and steady), a car came sliding down the hill to the
right and slid straight through the stop sign. Those of us going
slow and steady came to a stop well before the intersection and
watched said car (now sideways across the intersection) to see
what other amusing tricks it might perform. It proceeded to
sheepishly turn around and head back up the hill. Ah well,
probably for the best.

Central Maryland was lucky: it got warm enough that we just had
rain after Wednesday's sunrise. (Prior to that it WAS ice.) Now
it's howling fit to shred any sails those frostbite sailors care
to raise. (I truly enjoyed that right-of-way saying, thank you!)

While Maryland ALSO has the pedestrians-have-right-of-way-in-the-crosswalk, it's more like see-and-avoid around here. Grmph.

Be safe and warm everybody
Lauretta@Constellation Books

Talking about the weather-Harrisburg, PA

[(Anonymous)]

First, it snowed here Wednesday night into early Thursday morning. Then, it turned to a HEAVY rain, and washed a lot, but not all, of the snow away. Then it turned clear and breezy today. Tonight, it is supposed to remain windy, and the temps are supposed to drop down to about 18 degrees F. (For those of you in the UK and elsewhere, with a wind, that gets COLD, and I mean wrap-yourself-up-so-only-your-eyes-show cold.) It's still not as bad as the -50 degrees F windchills I experienced when I was a grad student in Duluth, MN, back in the 1980's, however.

And speaking of traffic in snowy weather: Duluth, MN, is built on a hill on the north side of Lake Superior. I observed that the rule of thumb in winter for drivers when snow/ice was on the roads was that anyone driving either up the hill or down the hill was ceded right of way by anyone driving across the hill, even if the person going up or down the hill had the STOP sign.

MCT in Harrisburg, Pa

[maddoxa.livejournal.com]

post pictures of these all over campus - they're wonderful!
http://www.the-perfect-present.com/Pages_Yaktrax/yaktrax_misspellings.html

[rolanni.livejournal.com]

Um, why? They don't make yaktrax for cars, and I haven't noticed a boost in IQ when I wear mine...

[maddoxa.livejournal.com]

I was thinking for the pedestrians.
but you're right, it won't make them smarter, just let them stop faster when they do notice the cars.

I _feel_ smarter when I can walk down the street instead of sliding, does that count?

[rolanni.livejournal.com]

I _feel_ smarter when I can walk down the street instead of sliding, does that count?

Definitely. And not falling down is a clear win. I don't do the falling-down thing well, at all.