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/sci/ - Science & Math

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Anonymous Tue Dec 31 02:30:32 2019 No.11266133 [Reply] [Original]

What are some basic HS level science misunderstandings people commonly have?
I'll start: increasing the surface area increases friction.

>>	Anonymous Tue Dec 31 02:31:58 2019 No.11266135 >>11266133 The Earth exerts a higher gravitational force on you than you do to the Earth

>>	Anonymous Tue Dec 31 03:03:55 2019 No.11266163 >>11266133 Temperature is the kinetic energy of the particles. Evolution makes animals evolve to adapt to their environment. Moon revolves around the earth. Quantum number s has to do with the particles literally spinning.

>>	Anonymous Tue Dec 31 03:08:46 2019 No.11266168 >>11266133 the body:machine, brain:computer, evolution:algorithm discourse is coherent entropy is real you see in 3-D

>>	Anonymous Tue Dec 31 03:12:51 2019 No.11266173 >>11266133 >increasing the surface area increases friction. I had this exact thought when I took highschool physics and to be completely honest, I still don't understand why it's wrong.

Anonymous Tue Dec 31 03:19:05 2019 No.11266179

>>11266173
well so, the exception is that any change in surface geometry that deforms either object is going to affect friction forces. 50lb on top of a needle, dragged across a shag rug is going to have different apparent 'friction'. this is why we assume that the two objects rubbing together are rigid

but in general, friction force is just equal to the coefficient of friction times the normal force. there is no place to plug surface area into the formula, so it doesn't matter.

>>	Anonymous Tue Dec 31 03:33:07 2019 No.11266200 >>11266173 >increasing the surface area increases friction. Installed bigger brakes and rotors on my 911 Porsche. Made a big difference in braking power. So, increasing the surface area increases friction must be true.

>>	Anonymous Tue Dec 31 03:35:00 2019 No.11266203 >>11266200 lots of different materials used for break pads - perhaps you just got a better one for your particular vehicle, totally independent of surface area

>>	Anonymous Tue Dec 31 03:36:42 2019 No.11266209 >>11266133 The rain in Spain mainly falls on the plain.

Anonymous Tue Dec 31 03:37:51 2019 No.11266211

>>11266179
>but in general, friction force is just equal to the coefficient of friction times the normal force
Well I know that, but this formula does just come out of nowhere and the coefficient is never derived empirically.

I have a physics degree. I just specialize in something totally different than this, and the issue never came up again after freshman year.

>>	Anonymous Tue Dec 31 03:42:14 2019 No.11266217 >>11266203 Are you saying if I installed smaller brakes using the exact same material, I would get the same stopping power as the larger brakes?

>>	Anonymous Tue Dec 31 06:08:27 2019 No.11266338 >>11266217 Yes but it would wear down the components faster

>>	Anonymous Tue Dec 31 08:39:08 2019 No.11266481 >>11266163 First one is not THAT wrong. Third one is a valid statement if you declare a point in earth your coordinate origin. >>11266168 >entropy is real What does that even mean?

>>	Anonymous Tue Dec 31 10:30:02 2019 No.11266630 >>11266338 If I ejected either a small or large drag chute from the rear of my car going at 60 mph, would the smaller chute give me the same stopping power as the larger chute?

>>	Anonymous Tue Dec 31 10:37:28 2019 No.11266641 >>11266630 >air resistance = surface friction I favor common knowledge questions to be able to post here instead of captcha.

Anonymous Tue Dec 31 10:47:51 2019 No.11266662

>>11266641
Friction is not totally understood, local variations in material surfaces play a much bigger role than what mu*N can really describe. Coming up with that mu is prone to experimental error. Also if you have a big break you can exert more shear force on a body. So in the basic vector analysis the breaking power will not increase. But I think the tensor analysis will reveal bigger breaks can shear more.

>>	Anonymous Tue Dec 31 10:57:26 2019 No.11266679 >>11266133 Planes fly because of Bernoulli's principle.

>>	Anonymous Tue Dec 31 10:59:51 2019 No.11266687 >>11266662 lol, reading comprehension is an elite skill these days. WHO THE FUCK CARES? that guy said air resistance is the same as surface to surface friction. Why are you trying to tutor me on friction coefficients?

Anonymous Tue Dec 31 11:11:55 2019 No.11266706

>>11266687
The man said a bigger chute will have more stopping power. True statement. Also, bigger brakes have more stopping. True statement. You projected your own comprehension that the poster believed air resistance equals surface contact friction. But really the poster was using an example where surface area matters for braking power.

>>	Anonymous Tue Dec 31 11:30:25 2019 No.11266728 >>11266133 >surface area increases friction It's not so clear this is a misunderstanding. http://threerockbooks.com/friction-and-rock-climbing/

>>	Anonymous Tue Dec 31 11:32:42 2019 No.11266734 >>11266163 pseudointellectual the post

>>	Anonymous Tue Dec 31 14:03:00 2019 No.11267088 >>11266173 increasing the surface area decreases pressure. this decrease in pressure exactly negates the increase in friction you'd expect from an increase in surface area.

>>	Anonymous Tue Dec 31 14:06:56 2019 No.11267103 >>11266163 >Temperature is the kinetic energy of the particles. It literally is brainlet

>>	Anonymous Tue Dec 31 14:08:36 2019 No.11267110 File: 244 KB, 470x422, 1575297974836.png [View same] [iqdb] [saucenao] [google] "Determinism and free will are in contradiction to each other"

>>	Anonymous Tue Dec 31 14:14:02 2019 No.11267127 >>11267110 >compatibilism lol pseud

>>	Anonymous Tue Dec 31 14:18:48 2019 No.11267140 >>11266211 >the coefficient is never derived empirically. What? The coefficient is only found empirically. I don't think anybody had ever calculated the theoretical coefficient of friction between two dissimilar materials.

>>	Anonymous Tue Dec 31 14:24:09 2019 No.11267156 >>11267140 I think he meant "the coefficient is never derived, only empirically"

>>	Anonymous Tue Dec 31 14:35:11 2019 No.11267181 >>11267103 ah, no. I believe temperature is proportional to the momentum of the particles. Therefore the energy is proportional to the temperature squared

>>	Anonymous Tue Dec 31 14:37:34 2019 No.11267185 >>11267181 What in the fuck "no"

>>	Anonymous Tue Dec 31 14:39:13 2019 No.11267190 >>11267181 >i believe You fucked up

>>	Anonymous Tue Dec 31 14:48:21 2019 No.11267212 >>11267190 cringe

>>	Anonymous Tue Dec 31 15:01:23 2019 No.11267234 >>11267212 This is a scientific discussion, your belief is irrelevant

>>	Anonymous Wed Jan 1 01:36:16 2020 No.11268347 >>11266641 Isn`t resistance same as friction. There is less air friction if I drive a sports car compared to a van. A re-entering space shuttle front surface area gets hot due to atmospheric friction.

>>	Anonymous Wed Jan 1 01:55:18 2020 No.11268372 >>11267103 touch a 20C warm piece of wood vs touch a 20C warm piece of metal

>>	Anonymous Wed Jan 1 01:59:45 2020 No.11268375 >>11268372 They only feel different because of the rates at which they conduct heat

Anonymous Wed Jan 1 02:17:41 2020 No.11268400

>>11267103
It is related, but it is not literally the kinetic energy of particles. The proper definition of temperature has to do with entropy and such. Different materials will have different average kinetic energies for the same temperature.

Why do brainlets always call others brainlets?

>>	Anonymous Wed Jan 1 02:31:15 2020 No.11268414 >>11268400 Different materials have different degrees of freedom. Don't project your projection of me

>>	Anonymous Wed Jan 1 02:43:51 2020 No.11268432 >>11268400 >entropy and such did middle class bongs figure out some way of aping their ruler caste recently that precipitated this speech pattern? What an infuriating idiotic tic.

Anonymous Wed Jan 1 03:06:39 2020 No.11268458 [DELETED]

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>>11268432
those who mimic people and behaviors which television and movies have presented as intelligent seem to be more common than the genuinely intelligent. furthermore the temperature of a surface is defined by the blackbody radiation it emits and some bullshit about the stephan boltzman equation and 4th root of flux which i don't remember all of off the top of my head.

>>	Anonymous Wed Jan 1 03:51:02 2020 No.11268526 >>11268375 exactly

>>	Anonymous Wed Jan 1 04:01:02 2020 No.11268547 >>11266706 No Anon, you're ignoring the context in which he posted completely to save face. My point stands. Reading comprehension is a lost art.

Anonymous Wed Jan 1 04:07:47 2020 No.11268557

>>11268347
No, not the same. The reduced air resistance is due to keeping flow around the vehicle more laminar. Then, resistance is proportional roughly to velocity, if I remember correctly. As soon as you get turbulent flow, it's roughly proportional to velocity squared.
This is also why it's most efficient to drive a car below ~130km/h, because normal cars start producing turbulent flow then, necessitating burning more fuel.
The heating upon reentry is friction plus resistance.

>>	Anonymous Wed Jan 1 04:49:48 2020 No.11268607 >>11266706 >Also, bigger brakes have more stopping. True statement. not a true statement though braking power is determined by friction between the wheels and the ground

Anonymous Wed Jan 1 04:51:43 2020 No.11268611

>>11266200
>>11266217
If the brakes are able to lock the wheels when braking that means that your braking force is not limited by your brakes. Now obviously this does not take into account such things like heat, your small brakes were probably getting too hot and loosing strength or something like that

>>	Anonymous Wed Jan 1 05:00:33 2020 No.11268616 >>11268557 resistance is always proportional to velocity squared

>>	Anonymous Wed Jan 1 05:39:07 2020 No.11268672 >>11268616 https://en.m.wikipedia.org/wiki/Drag_(physics) Very low Reynolds number: Stokes Drag. Proportional to v. I was wrong with my example though. It's when drag becomes larger than tire-to-road friction.

>>	Anonymous Wed Jan 1 05:45:07 2020 No.11268679 >>11268672 oh shit i always though it was just proportional to velocity squared, that's pretty fucking wacky that the difference between laminar and turbulent flow is so huge

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