80%. I have shamed my family.
The ones I missed were mostly because of semantic differences between terms as used in physics and in everyday use (“force”, “velocity”, “vapor”).
90%. Not bad for someone without a science degree and no physics education since school.
There were a few tricky ones in there. Like the water vapour one. And the missing ‘for’ in question 14 didn’t help. Especially when it talks about ‘her perception’, which is hardly a scientifically measurable attribute.
So where’s Chronos? Did he post?
Just to help folks out on this page, here’s the “easy-to-read” version of the test on a free geocities website: http://www.geocities.com/internet_web_surfer_dude/physics.htm
62.5%. I don’t feel too bad about it. I never took physics in high school and the only class I took in college was on cultural conceptions of physics. I enjoy reading popular astronomy and astrophysics books but there is a reason I don’t attempt anything more complex than that. I’d like to go back and take some classes, but I’d have to start at the very beginning, which is a little intimidating.
meh
I have never taken a physics class, so my score was 52%.
Well, here is an answer from someone who also missed the voltage question.
The electrons are moved by the force that is exerted on them by the electric field. The electric field intensity is E = F/Q, F is the force and Q is the magnitude of the charge that is placed in an existing field. So for a given charge, like that on an electron, the force is the field intensity times the charge on an electron.
As Stranger said the real picture of how electrons move in a wire is complex but a simple explanation is like this. Assume a conductive wire between two points. An electric field originating from a charge suddenly placed near one of the points propagates at the speed of light in the medium in all space around the charge including down the wire. As soon as the field reaches an electron in the wire it starts to move so all electrons in the usual case start to move virtually at the same time.
A crude analogy is a tube filled completely with a liquid. If a piston is placed in one end and rapped with a hammer it generates a pressure wave in the tube that rapidly propagates down the tube and the effect is felt at the other end almost immediately even though the fluid in the tube has actually moved very little.
I’m eliminating the spoiler boxes in on the assumption that anyone who’s read this far is already tainted.
Friction is indeed a force between two surfaces in contact. It is the result of interactions between the surfaces and is dependant upon the force normal to the surface and the coefficient of friction, which is generally taken to be a constant (or two constants, one for initial movement and one for dynamic movement) in basic physics and mechanics textbooks but is in fact significantly more complicated than that.
In your example of the roller skates above, flinging your arms backward isn’t going to result in net movement of the system (you)…unless your arms come away from your shoulders, in which case you are going to have far more problems than coping with an understanding of physics. (For instance, you won’t be able to operate your digital watch.) What you’ll find is that in flinging your arms backward your feet might move slightly forward, but in order to remain balanced you are going to have to bring your arms back forward, or shift your weight forward or somesuch, which will bring your skates back to their initial position. In the end, the center of mass of the system can’t move without pushing or pulling against something else. In reality you might be able to “shrug” your way forward a few centimeters at a time, but that still requires cancelling your inertia against friction at some point during the motion.
Stranger
15 mph going east cancels out the 15 mph going west. 15 mph going north cancels 15 mph going south. Mathematically, one direction would be +15 mph, and the other would be -15 mph, so they cancel out.
92.5%. I went through it too fast. If I’d taken my time on each and every question, I might well have aced it. Then again, I might have done worse.
57%
Most of the stuff I got wrong was where I didn’t know the scientific meaning of velocity or stuff that the explaination said was a common misconception.
87.5% Last class, 1982. As with others, a couple of pitfalls due to strict definitions and a few others just brainfarts. Still, hell, I wouldn’t be surprised if their alleged 75% “minimum” is likely superior to the physics knowledge of most HS graduates anyway.
Missed:
12 - Susan v. Earth. Just plain missed it
15 - Negative acceleration: &^%$# vectors! But their explanation, in this and in others, that books/schools “teach it wrong” gets a hearty one-fingered salute from this side. More on that later.()
17 - circular track: furshlugginer vectors, again
18 - Tiptoes. Difference between “force” and “pressure”, obvious and blanked out completely.
29 - Clouds. OK, they got me to rights, indeed, to a real phycisist, “water vapor” IS correctly speaking the entirely gaseous state of H2O, visible “cloud” is suspended condensation. Fine, that and 50 cents buys them a cup of coffee I spat into.
Feel pretty good about avoiding the Voltage pitfall, having remembered that it was taught to me in HS and college that Voltage was electric potential and that “electromotive force” was an archaic term from grade-school.
#8 Energy-thermal v. energy-mechanical did not fool me. I cannot possibly convert 1000J of thermal perfectly into 1000J of mechanical no matter what. It’s really a restatement of #6 when you think about it.
(*)Back to “more on this later” . All those engineers with <92% scores? Engineers (and more than a few of us in other disciplines) are practical-applications people, and grow used to using results-oriented shortcuts even if they do not match the strict terms of theory. Some of these Q’s dependend on a fanatical adherence to exact approved terminology… that does not have much to do with whether or not the roof of the building stays up.
Also, the textbook writers and non-college schoolteachers probably would think it’s a step of progress inthe right direction if the average student thought “negative acceleration = slowing down”, as opposed to “= moving backwards” or even “= something they put thru the warp drive in Star Trek”. Or that clouds are made of H2O in SOME form. And they’ve been teaching “electrical potential” instead of “electromotive force” for lo so many decades now… The condescencion I’m sure they could do without.
Also they say “monkeys would have an average score of 50%”. That’s what several runs with random monkeys should approach, but for instance a totally unthinking answer of all-F would give you a score of 67.5%, more than halfway from the “monkey” to the alleged minimum literacy of 75%. That condescencion we ALL can do without.
Wrong example. In the question they’re talking about a car. The propulsion is applied from the engine thru the tranny and axle to the rotating drive wheels, and it’s the friction between the tire and the road that makes that rotation be translated (by action-vs-reaction) into forward or backward motion. No friction, and the wheel simply spins in place with no net movement. That is the sole self-propelled mode of the car’s operation.
Your example would apply if the car’s wheels were unpowered and you were trying to move it by flapping a couple of boom sails attached to the roof.
Take off your skates and stand in rubber shoes. The action-reaction force of friction between your sole and the floor makes the attempted backward stroke of your drive leg translate into forward motion. No friction and you’re going nowhere (and looking like Michael Jackson while at it). The fact that you’re flexing your limbs backward and forward does not impart any net motion to you w/o some resistance to work against.
60%
Never took a physics class in my life.
100%
A few questions I couldn’t have answered with what I remember from school (7 years ago), but I rememberd discussions on the SDMB about those things.