Positive and Negative Torque

How to tell whether a torque is positive (counterclockwise) or negative (clockwise.)

[@annamachado6618]

you helped me understand this better than any other resource, thank you!

[@robertcruikshank4501]

Thanks! I'm glad it helped!

[@makethomas752]

Thank you for this enlightening video. Its been a few years since I learned the basics back in college. I recently started to write my old notes and practise calculation down and found out that I forgot how to determin if an axial force/torque is pos or neg. After hours of searching I saw your video and when you mentioned the wheel I was finnally clear to me again. My professor explained it to me the same way but I didnt made an notes because I was young and thought I will never forget the basics.... Thank you

[@tereshtaymor1404]

Bro your a life saver❤

[@mohamedfarhat2313]

Thank you very much, sir! I really needed this video for my grade 10 final exam!

[@clems6989]

Great job !

[@robertcruikshank4501]

Thank you!

[@Qwe-vb3vv]

Thank u sir. .this concept is very helpful in jee exam... Love from India

[@dreamwarrior153]

Thank u very much sir i understand the concept very clearly 🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻

[@robertcruikshank4501]

Excellent! Happy to help!

[@HeadSpaceInspire]

thank you for the nice explanation. I wonder if the torque on G should be negative if we follow your explanation of the radial line on points B and C? thanks!

[@robertcruikshank4501]

No, the torque of G is positive. If you draw a line from the origin through G, G is pulling below that line, which is counterclockwise, so positive. If you use the line of action, it is the same one as for force F. Pulling down on the left is counterclockwise positive torque. So is pulling right on the bottom, pulling up on the right, or pulling left on the top. I hope that helps.

[@petworldin]

thankyou very much ...,,,love from india

[@petworldin]

sir I`m a medical aspirant, in India we have to give a pre exam for admissions on 40k government seats,, in a competition of 1.9 million aspirant, for this we have to solve 180 question in 180 minutes of physics, chemistry, botany, zoology,, there are 45 questions from each section,, but sir point is that please give me a advise how to solve 45 question of physics in 35 minutes,, mine syllabus is whole basic physics except quantum physics. plzzz help me I know my English is not so well but I think you will understand what I wanted to request you Sir.. plzzzzzz help me, your one advise may be helpful for my life... plz help me...

[@robertcruikshank4501]

Physics textbooks often have "concept questions" before the regular exercises at the end of each chapter. Knowing those can help a lot with test preparation. Good luck to you!

[@petworldin]

Thanks a lot 🙏, for your instant help 🙏 😊

[@freefire-fk4hf]

sir why we take clockwise torque negative and anti clockwise torque positive

[@robertcruikshank4501]

It is consistent with the right hand rule. Originally an arbitrary choice but now it is standard convention.

[@sudip3852]

sir I have a doubt, if see from one side of a rotating wheel its rotate CW but for same wheel if see it from another side it rotate CCW, then how we know its positive or negative or from which side we consider

[@robertcruikshank4501]

The direction you view from should be specified in the description; some problems fail to state it clearly. Regardless, one physical thing happens, which can be described in different ways. In the 3D version, torque is a vector, and "counterclockwise" means "out of the board" and "clockwise" means "into the board". Sometimes to solve a problem it is necessary to clear up the ambiguity as to which side you are viewing from. It's much like choosing a coordinate system: you have to be consistent, but you will get the right answer regardless of choice.

[@why-vf1cc]

Sir why anticlock wise is +ve angle?

[@robertcruikshank4501]

That's the standard developed. It matches trigonometry class. True enough, the standard was arbitrarily chosen, like deciding screws go in when turned clockwise, or direction of current is opposite the flow of electrons, but it is standard.

[@dreamwarrior153]

Sir, why torque is r x fand not f xr

[@robertcruikshank4501]

It is because of the way we defined cross product and torque. We could have defined it in the other direction instead, but we have to pick a standard and stick with it. We chose "right handed" coordinates.

[@dreamwarrior153]

@@robertcruikshank4501 sir, please explain it with some example