h a l f b a k e r y
Results not typical.
idea:
add, search, annotate, link, view, overview, recent, by name, best, random
meta:
news, help, about, links, report a problem
account:
Browse anonymously,
or get an account
and write.
or Create a new account.
|
|
|
A lot of tests in the hard sciences are fairly of the fairly boring pen and pencil type. Physics tests don't have to be that way. The problems could easily demonstrated in short video clips instead of words making the test more interesting. For instance, there could be a crowd scene where people are
shooting their weapons straight up in the air to celebrate something. This question would appear beneath it - why would it be a bad idea to join this crowd based on physics? Or one of the hundreds of suggested perpetual motion machines could be shown in operation. This question would appear beneath it - without mentioning any laws of physics, explain why this machine will eventually stop. Almost every law of phsyics that is taught could be turned into a video scene that would make taking the test a lot more interesting. And it would also show whether or not the students truly understood the application of the laws involved.
[link]
|
| |
While I agree that audio-visual techniques are a great teaching aid, I don't think that physics is short of good experiments. Electro-magnetism, equations of motion & mechanics, and to a lesser extent wave theory all have nice little possible demos. |
|
| |
Um... Because of the noise of all those rifles going off at once? |
|
| |
And this would discriminate against all the non visual learners out there. (waves hand) I would have to walk in and just say "give me the F" I am NEVER going to be able to figure out what the significant factor is on a video like that. |
|
| |
Is the major problem gathering in crowds? Celebrating? Owning weapons? Wasting ammunition you should be spending on food? Breaking laws against disturbing the peace? Bringing an AK-47 to an AR-15 party? Wearing the wrong colors? |
|
| |
are you truly saying that you couldn't figure out the *most obvious* application of basic physics to a bunch of people shooting rifles into the air? Perhaps the question could be, "if the bullets are travelling at 1000 fps, how long until they come back down?" |
|
| |
The teacher will be able to point students in the right direction, maybe. |
|
| |
No, I would miss it entirely. The bullets might leave the gun at 1000fps, but they return to earth at under 150fps (terminal velocity, don't you know) so the bullets are no more a danger than a sudden hailstorm. Knowing that I would discount the rifle fire into the air and look for something else. Perhaps people in the crowd are smoking cigarettes, far more dangerous. |
|
| |
And how is a teacher going to direct students during an exam? If they speak in any way they are changing the test conditions. Which is why I always remember tests being administered by grad students, who just handed out papers and then sat impassively. |
|
| |
Physics is very much about visualising how the real world works and understanding the maths beneath it. Using video in teaching physics will no more discriminate against non-visual learners than it would against visual learners as the non-visual element will remain core to the subject. I'm just not sure that it will work in an exam situation. |
|
| |
This would be fun if the visually orientated students had to mime the answers. |
|
| |
//Who wants to learn physics!? Step right up// [Carney].... //Go Coney Island Whitefish!// [Fry] |
|
| |
//why would it be a bad idea to join this crowd based on physics// Well, based on chemistry, you'd know that the exothermic reaction in the cartridge would make the ejected shell hot, and you wouldn't want one to hit exposed skin. |
|
| |
co - I guess we'd just have to give points for any answer that matched a law of physics with the premise of the question. |
|
| |
From a student's point of view, it would be nice if there were video demonstrations along with the written question, just to clarify exactly what is going on. It seems like half of the effort of solving some problems is in trying to figure out what exactly is happening in that diagram. Just a 3 second clip on a loop of whatever mechanism or movement you are studying would help out immensely while not discriminating against non visual learners (if it would just confuse you, just don't look). |
|
| |
What level of tests is this meant to apply
to? Fine if it's for small children, and it
might be good fun. But what would be the
point of doing this at any higher level?
I'm not sure you've really got the idea
behind physics or behind exams. |
|
| |
//based on chemistry, you'd know that the exothermic reaction in the cartridge would make the ejected shell hot, and you wouldn't want one to hit exposed skin// |
|
| |
That law of physics was why I always attempted to get a slot on the far left side of the shooting range when I needed to practice for the Navy. |
|
| |
Of course, then I'd get moved over. I thought it was bad when one guy hit me upside my head. Then one day, I got hit by two shells in a row. One got stuck on the back of my neck until I shook it down to my butt crack. The very next one slipped down the front of my shirt, and somehow lodged in my belly button. |
|
| |
Luckily for the guy standing next to me, I had just gotten my lat bullet off when that happened. |
|
| |
The world according to google - |
|
| |
Velocity of a bullet = sqrt ( (2 * W) / (Cd * r * A) where Cd equals the drag coefficient (.295), r is the atmospheric density, W is the weight and A is the area of the object. A bullet going up at 670m/s would come down roughly at 112 m/s, which could kill you. |
|
| |
A more interesting test for advanced students would be to show the same scenario, pose the same question, and accumulate points based on each answer that correctly tied a law of physics to as many risks as the student could identify. |
|
| |
//Velocity of a bullet = sqrt ( (2 * W) / (Cd * r * A)//
You sure about that? There doesn't appear to be any initial velocity term there. |
|
| |
Ok, an 8gram projectile at 112m/s is 896 newtons. Lets round up and call it 1kN. or the same as a 1kg weight moving at 1m/s Or a 1/10 kg moving at 10m/s. About what you would get from a baseball dropped from five feet above your head. Ouch, but not dead. |
|
| |
//an 8gram projectile at 112m/s is 896 newtons//
F=ma - you quote a velocity. |
|
| |
Having twice in my life been close to bullets when they came back down (idiots on New Years Eve), I can promise you that they can have sufficient force to injure or kill quite readily. And [Galbinus] 896 N on a 63mm^2 bullet is a lot more dangerous than on a ~3000mm^2 baseball. |
|
| |
They did this one on mythbusters. The result they got from experimentation was that the bullet would break skin, but not fracture skull. |
|
| |
Then they heard from a doctor who treated two verified cases of "I know not where" bullet wounds, one fatal. The conclusion was that straight up bullets have a chance to bleed all velocity, but bullets fired at any significant angle retain too much horizontal velocity for safety. The person accidentally killed was a long ways from the shooters. |
|
| |
You also have to consider that all bullets are not created equal. A pellet from a shotgun hitting you at 112 m/s won't do much (it feels like rain, from personal experience), but a cannonball hitting you at 112 m/s most likely will do some damage, yet both are projectiles. It's all about the kinetic energy that they possess. |
|
| |
[GC] I still don't get your assertion that a bullet "is" x Newtons. An 8g bullet at 112m/s has just over 50J of kintetic energy. No Newtons involved, until it decelerates. |
|
| |
Did I flip my units in the middle of the night? I meant gram-meters/second. Measure of momentum. Sorry, I have been ill for a few days. |
|
| |
Basically my point was that if you fire a bullet up into the air, it is little or no danger to you and those close to you. If you have fired vertically enough, it will bleed off enough velocity to not be more dangerous than a similar size stone dropped from a building above your head. If you have fired other than vertically, it will land at some distance away and not be a danger to those close to you. |
|
| |
The core question in the original invention is "What is the greatest apparent danger in this photo/video, to the people in this photo/video?" And my reassertion is that it is NOT the bullets from their rifles returning to earth and hitting them. Thus it must be something else. |
|
| |