Torque - An application of the cross product

[8644371]

foot-pounds

[foot] = vector; [pound] = scalar

♪♫Mass is a scalar!♪♫

Scalar × Vector = Vector-with-a-magnitude-multip­le-to-the-scalar

[aidenator00]

I like how you make much more sense and are clearer than my college professor. Thanks PatrickJMT! (You should consider SI units).

[kimmrock]

i think you're one of those people who actually deserve the youtube partnerships unlike those useless vloggers who talk about nothing...

[lucpilon1]

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

[magicalchair]

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......

[GBoss704]

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

[s0nnyburnett]

"Plug it in" XP, substitute the values

[o0Vox]

The magnitude is just the force of the rotating body. T=Ia where T is torque, "I" is moment of inertia, "a" is angular acceleration. Remember F=MA ( That essentially applies to translational motion), T=Ia (Applies to rotational motion). The moment of inertia is essentially the mass of the rotating object sort of...lol. I have a slight idea on what moment of inertia is. but its essentially the angular mass....hope that helps......just know there is not actually a force coming out or in

[janskwaired]

Since it has "9 inches" next to the wrench, it looks like a penis

[divvy1400yam600]

@ivvy: you are not wrong...you are right...I think lol

[divvy1400yam600]

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 ?

[o0Vox]

@divvy1400yam600

Torque is a very hard concept to understand. Here is my view of it. I may be wrong but it makes since to me.

First off the direction of the "torque force" just defines the axis of rotation. If you are looking down at the X-Y plain, angles going counterclockwise are positive. The Z axis is coming at you. That Z axis would be your axis of rotation and would be positive. If it's clockwise it's negative.

(Ran out of characters, will finish in new comment)

[olafzijnbuis]

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.

[patrickJMT]

@olafzijnbuis okie dokie

[olafzijnbuis]

@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.

[mgm546]

@olafzijnbuis you realize this is a basic physics/math tutorial, not a cutting edge technique to fix a car, right?

[chadbowman0]

Why would anyone do physics with standard units? I live in America. 

[Keh0ol]

@chadbowman0 terrible ain't it? i honestly can't watch this

[Cyphlix]

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?)

[isam1335]

I'm gonna continue my study in us next spring 2011..n i still feel like an idiot with those non-SI units ! lol

[kickinapouch]

OMG YOU DO PHYSICS TOO?

[mahmoudahmed1992]

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.

[JonProce]

@mahmoudahmed1992

It depends where you are, in any kind of mechanical application in north america torque is always defined in ft-lbs, at least on airplanes and cars which are what I'm familiar with.

[Keh0ol]

@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 :)

[mahmoudahmed1992]

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.

[boatyboatrite]

Aaaaah, why are you not using metric units? You do everything else so well...

[soulblazer91]

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?

[drumcoverboys]

naw, torque is just a representation of a force applied to a point over a distance. Not to be confused with work though which has the same units of N*m of Foot*pound, which is considered Joules. Torque is just a rotational force over a distance pointing in or out of the page

[heiismail]

What is the unit of torque

[starsiegeplayer]

@heiismail the unit of torque is force*distance. That can be foot-pounds or inch-pounds or Newton-Meters or Newton-centemeters etc

[kevthehover]

Glad i dont have to change a wheel nut LOL

[patrickJMT]

AAA for like $20/yr is the only way to go

[SweetPizka]

I was blinded by my stupidity and now I can see. Merci.

:p

[illa2015]

thank you!!

[wyzt]

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.

[graffiticrime]

nice demonstration ft/lb is the key. 9 inches out of 12 inches or one ft is .75....

[Laingalang]

Really useful but argh at the non-SI units :'(

lol

[patrickJMT]

viva america!

[Laingalang]

haha lol - you got me good there :)

[RapidFireAlgorithm]

Nm rules!!!

LOL

[MRIYBR]

wasn't this DOT PRODUCT ?? isn't cross product all about finding another vector perpendicular to 2 vectors?

[patrickJMT]

no, we found the cross product, then we found the magnitude of that vector

[muddwell]

yeah, nothing like obscure conversions.

[CascadeHope]

Really helpful videos! I used them to study for my Midterm, and I think I'm going to do pretty good now, because of them :D

[5i13n7]

Awful wrench ;) Good explanation though, thanks!

[patrickJMT]

yep, pretty terrible : )

[LTF85199]

thanks Patrick, Simple and understandable,

[jr10487101]

It would be nice if you could use SI units.. ?

[dondean517]

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.

[Golfmasta]

lol! i was looking at ur video and my mom came on and thought it was a penis!

[patrickJMT]

sweet. your mom was projecting.

[goosefrabbas]

lol wut?

[patrickJMT]

projecting... a term that came from freud i believe!

[uz4ir12345]

nice pic

[patrickJMT]

ya! not the best : )