Torque - An application of the cross product
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- Опубліковано 16 вер 2024
- Thanks to all of you who support me on Patreon. You da real mvps! $1 per month helps!! :) / patrickjmt !! Torque - When you tighten a bolt on the tire of your car, you are using torque! An application of the cross product involving torque is shown. In this video, I calculate the magnitude of the torque vector.
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I like how you make much more sense and are clearer than my college professor. Thanks PatrickJMT! (You should consider SI units).
Thank you! I've been trying to think of an application for the cross product and I had no idea. This is brilliant
thank you soo much for teaching me and multiple classmates of mine how to do these problems, your more useful than our teacher, we watch your videos on the board all the days he is away :P
Calculus & Vectors exam tomorrow, this saved my life
Probably an issue of me not knowing American measurement system, but why did he divide 9 by 12?
12 inches in a foot so I am putting everything in terms of feet
lol yeh i was initially confused as well
maybe one day we'll all use metric and all live happily ever after
i think you're one of those people who actually deserve the youtube partnerships unlike those useless vloggers who talk about nothing...
@heiismail the unit of torque is force*distance. That can be foot-pounds or inch-pounds or Newton-Meters or Newton-centemeters etc
Pretty amazing how much a good explanation helps...30 minutes of a teacher explaining who knows what...versus understanding it in a quick 4 minute video, haha. Thanks! I need better teachers.
know what's fun to do? play a bunch of these videos at once in different windows and listen patrick talk over himself. Thanks for helping me study for finals......
@patrickJMT
Hello Patrick. Later I checked out some of your other video's and a started to look at the videos on tour website. Perfect teaching stuff. I needed it to do some vector algebra. Sure helped me out. Thanks, Olaf, the Netherlands.
Nice video, helped with an upcoming midterm ... but here the wrench slips off! haha Keep up the good work.
Great video, bit confused about the right hand rule, could someone explain, when it comes to torque does the direction your thumb points have any relevance? or is this all just a sign convention? I'm guessing its more useful for things like magnetic fields?
thanks Patrick, Simple and understandable,
@patrickjmt sorry didnt know that comment was posted two more times... love your videos btw... helped me pass cal 2 last semester :)
i Think ur supposed to change the pounds to newtons by multiplying by 9.8. and our teacher told us that torque is measured in newtons per meter(N-m). so u would connvert 9 inches to meters.
You guys realize that his videos are calculus related right? This is likely a multivariable calculus video, not necessarily a physics video. Basic Physics classes are much simpler, in multivariable calculus they go much further into vectors. This is the beginning of the course.
no, we found the cross product, then we found the magnitude of that vector
great explanation! terrible looking wrench though...
you're right
looks ok to me.
Thank you
I am genuinely confused
If the cross product mathematically describes this situation then the resultant force is either into or out of the screen.and does NOT cause rotation.
Rotational force is required to undo the nut.
My instinct tells me that the resultant force should be tangential to the end of the spanner (wrench 2U)
Why am I wrong ?
@mahmoudahmed1992 the unit of newton is kg*m/s² so multiplying the weight in pounds by 9.81 (m/s²) isn't going to cut it :)
could you do one with a pulley. I was in physics class and I didn't understand how he got the sine of theta. I have read my book but I just can't see how you figure out where theta is supposed to be. Thanks.
AAA for like $20/yr is the only way to go
viva america!
The wrench would work a lot better if it would fit OVER the nut. This wrench is useless.
Another thing is that the torque can only push the wheel agains the hub because the use of screwthread. The pitch of the thread is what 'converts' the torque to a FORCE to hold the heel to the hub.
yeah, nothing like obscure conversions.
i got 0.75 * 20 * sin(80) = -14.9083298 from calculating in a google search (obviously its not negative, but where did the .77 come from?)
thats just the general torque equation, why is the cross product needed? try computing it without using that eq and going into the cross product chart
A little late but in multi variable calc this is a concept they teach.
please also explain how to find direction
I don't understand how you can use both the length in feet and force in pounds as magnitudes in the same problem. Don't we have to convert 20 pounds into feet somehow?
1:34 9 Inch wrinch
so would that also be the force of the nut coming off the bolt? (with the opposite direction of course)
@ivvy: you are not wrong...you are right...I think lol
thank you!!
TYSM
Thanks for the VIdeo!!
you should use SI units, its not like mechanical engineers are this video to learn about torque, at least I hope not. but yeah most of your viewers are students, and most colleges teach this in SI units.
I believe the Torque should should be negative, that is because the force is going in the clockwise direction.
The problem was "find magnitude of torque" which is always positive. Formula could have been |T|=|r||F||sin θ|
Anyway, rather than usually, say traditionally. Clockwise is just the torque vector pointing away from you. That's negative only because you traditionally insist that the z axis is pointing at you.
Biggest problem people really have with this is they don't realize when this positive/negative info is missing.
It's not in the vectors. They don't know. It's not in the angle. It doesn't know. It's in the original problem. It's knowing that the r vector goes first in the cross product. Or you can look at this and realize it will move clockwise. Just remember that's negative and insist that your answer agree with that. Do both and you can check your work.
Unless you were just asked for magnitude. Then it's always positive.
What if there is more then one vector adding torque? Look at them one at a time and add them up.
A torque vector tells you three things The direction of the axis of rotation, the force of that rotation, and where to stand to see the rotation as moving clockwise (at the tail).
"Plug it in" XP, substitute the values
Shouldn't the angle be the angle between a and b, which in this case are r and F, be 100? If the angle of the force is 80 (complementary side), then the angle between the vectors should be 180-80 = 100, right?
MagicDr I dont think the "Sin(theta) = 180 - deg" is entirely correct. I also have been using the "180 - deg" but, after using the direct sin(deg) calc function recently, I get a completely different answer. So, Im confused on which one is right. Also, Im wondering if you have to decide on the conversion based on the measurement system used. e.g., MKS and CGS.
(0.127m)(16N)("sin(60) = .866")= 1.759 (1.8 Nm) (0.41 f lbs)
(0.127m)(16N)("sin(180-60)= 120")= 243.84 (244 Nm) (55 f lbs)
??
MagicDr He used the calc function of sin(80). So, maybe the CGS system uses the calc function and MKS uses the sin(180-deg) and sin(y/r) function/identity?
Idk, Feedback welcome.
What is the unit of torque
units 9 inches is 3/4 of a foot
sweet. your mom was projecting.
Why aren't you using SI units?
Hey bro`! Hope you're having a lovely day on the internet superhighway.
In anycase,
I'm confused as to why you had to convert the vector 9inches into (.75)?
Also can you explain why you're using the angle 80 degrees instead of 100 degrees (isn't that the value of the angle actually inside the wrench vector and vector [F] ?
putting this here in case anyone else sees it. i know its been... 9 years lol. he converted the magnitude of 9 inches into 0.75 bc he was converting from inches to feet. 9 inches is 3/4, or 0.75, of a foot.
@olafzijnbuis you realize this is a basic physics/math tutorial, not a cutting edge technique to fix a car, right?
What are lbs?
pounds
ya! not the best : )
Trolls, trolls, trolls (ACDC). He said never mind, we are putting the bolt *on*; meaning he realized that.
Why would anyone do physics with standard units? I live in America.
Glad i dont have to change a wheel nut LOL
projecting... a term that came from freud i believe!
GOD!!.
OMG YOU DO PHYSICS TOO?
wasn't this DOT PRODUCT ?? isn't cross product all about finding another vector perpendicular to 2 vectors?
we found the magnitude of that vector. the dot product would have a cos, not a sin.
okay scratch that first problem I get the equation's in foot/pounds
I'm gonna continue my study in us next spring 2011..n i still feel like an idiot with those non-SI units ! lol
wyzt is right lmao my teacher was talking about this stuff just the other day didnt understand shit all in that whole hour long lesson then come watch this 4 minute video and i understand it perfectly?:P damn teachers
@olafzijnbuis okie dokie
W o w, i t ' s g o t a b i g *t o r q u e*.
Why we can't use Cos tetha in Torque?
nice pic
yep, pretty terrible : )
Awful wrench ;) Good explanation though, thanks!
right tighty lefty loosy. You won't ever get it off turning it that way.
@chadbowman0 terrible ain't it? i honestly can't watch this
i Think ur supposed to change the pounds to newtons by multiplying by 9.8. and our teacher told us that torque is measured in newtons per meter(N-m). so u would connvert 9 inches to meters.