what a great lecture, respect!!! The best thing about your lectures for me is that you are giving perfect examples from daily life. Thank you for all your efforts:)
Fun fact Dr. Anderson, I am a mechanical engineering student at UC Berkeley, and whenever I forget basic concepts in physics, I refer back to your RUclips Channel. Cheers!
Thank you Prof. Anderson for your contribution to our understanding of this concept. And now I received further proof that these videos get mirrored before publication :)
I always use to say lefty-loosey righty tighty when I lock my car door manually, but then my drivers side car door broke and when I fixed it it became lefty lockey righty-unlockey lol
Karina Blanchard, Love it. Stealing it. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A
In Tamil Nadu I can't find a Physics Professor like him. (Searching for 5 years, from the day I joined Engineering but luckily I found *Anderson😎* in RUclips fews weeks before)
does the angle between force and the radius vector is always constant for a particular torque....if it is so how can the bolt rotate in the same plane containing the force and the radius vector as its angle will be continuously changing
The torque formula is an instantaneous event. This isn't like work, where it is a cumulative quantity. Take the force, the radial coordinate, and the angle, all at the same time, and that gives you the corresponding torque at the same time. In an example in a non-calculus Physics where torque is applied through a rotation angle, they will usually give you a setup where the angle in the torque formula can remain constant. Both force and radius vector may rotate, but they both rotate the same, and the angle between them remains constant. One example where it is NOT constant, is in a crankshaft of an automobile engine. At bottom-dead-center and top-dead-center, the piston cannot apply any torque to the crankshaft, because the force from the piston points directly through the center of the crankshaft, and the sine term is zero. It is much more effective after the shaft has rotated 90 degrees, and the connecting rod has better leverage on the shaft. This is part of the reason why gasoline engines need electric motors to assist with startup.
I was wondering about direction of cross product. consider if we push the door in outward direction, with force perpendicular to the length of door. the force is in forth direction and moment arm is perpendicular to it, then if we use right hand rule than door should move upward!!! I am confused about this
Suppose the hinge is on the left side, and you open the door opens away from you. You push forward. The radius vector points to the right. The torque on the door is (by our convention), pointing upward along the axis of the hinge. The direction of angular quantities is defined in the direction of the axis of rotation, and doesn't necessarily correspond to anything physical happening in that direction. Think of it as the direction that the motion *isn't* happening, because motion is happening in the other two directions, and there is no clear reason to choose either of them. It is an arbitrary convention that we define it with a right-hand rule. We could've just as easily defined it with a left-hand rule.
I know you take the mirror image to show the lightboard correctly, but it causes another ambiguity. You show your left hand while telling about the right-hand rule.
I always assumed torque was in the direction of motion, but I guess it isn't. So, wait, angular momentum is also perpendicular to both r and p, so is torque and angular momentum the same thing?
Torque and angular momentum are not the same thing, but both have a direction given by the right hand rule. Think of an object laying on your table. If the object is being twisted in the clockwise (CW) direction by a torque, then the direction of the torque is into the table. If the object is being twisted in the counter-clockwise (CCW) direction by a torque, then the direction of the torque is out of the table. This is the ole "Righty tighty lefty loosey" phrase that applies to screws. Turn it to the right (CW), it gets tighter because it is going into the table. Turn it to the left (CCW) , it gets looser because it's coming out of the table. (Sidebar: this only works on normal right-handed screws. Very occasionally, you come across left-handed screws and everything is reversed.) Angular momentum has the same rules for direction, but of course different units since angular momentum has to do with rotational velocity, not rotational force. Hope this helps. Cheers, Dr. A
+xMinimalistic You can use your left hand, but when you're done you need to add a minus sign. So your thumb will point in the opposite direction. Cheers, Dr. A
Alex, Yep, I need to use my left hand for all "right-hand rule" demonstrations. And on top of that, I have to remember that vectors towards me (out of the page) are actually flipped (into the page). The right hand rule was the trickiest part of using the Learning Glass. Cheers, Dr. A
Sharon 92075, My career as an artist is in jeopardy. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A
Think of it as the base of the door or cross section. We are dealing with lines and directions so he has simplified an acual door. I must admit I was reminded of Homer's appraisal of Kirk Van Houten's sketch though ("That's a door?!!!") 😆
![Young Nudy - John Wayne (feat. Metro Boomin) [Official Video]](http://i.ytimg.com/vi/NY8HnYYo2fo/mqdefault.jpg)
what a great lecture, respect!!!
The best thing about your lectures for me is that you are giving perfect examples from daily life. Thank you for all your efforts:)
Fun fact Dr. Anderson, I am a mechanical engineering student at UC Berkeley, and whenever I forget basic concepts in physics, I refer back to your RUclips Channel. Cheers!
Excellent good vibes physics lectures!! Making it easy to comprehend.
Thank you Prof. Anderson for your contribution to our understanding of this concept.
And now I received further proof that these videos get mirrored before publication :)
THIS WAS BEAUTIFUL ! GOOD GOSH. I feel like a fool.... Thank you. Excellent video. Thank you very much.
Not sure why you feel foolish, but thanks for the feedback! And keep up with the physics.
Cheers,
Dr. A
This is magnificent. What a great teacher
Harry,
Thanks for the comment, I really appreciate it.
You might also like my new website: www.universityphysics.education
Cheers,
Dr. A
thanks for uploading them .. very helpful
You are very welcome.
Cheers,
Dr. A
Great lecture
I always use to say lefty-loosey righty tighty when I lock my car door manually, but then my drivers side car door broke and when I fixed it it became lefty lockey righty-unlockey lol
Karina Blanchard,
Love it. Stealing it.
Thanks for the comment, and keep up with the physics!
You might also like my new website: www.universityphysics.education
Cheers,
Dr. A
Very well explained ;) thank U !!!
Thanks for the feedback.
Cheers,
Dr. A
In Tamil Nadu I can't find a Physics Professor like him.
(Searching for 5 years, from the day I joined Engineering but luckily I found *Anderson😎* in RUclips fews weeks before)
Viper! !,
Glad to hear it!
You might also like my new website: www.universityphysics.education
Cheers,
Dr. A
@@yoprofmatt 😍 Thanks Professor
thank you
Dik Jbr,
You're very welcome. Glad you're enjoying the videos.
You might also like my new site: www.universityphysics.education
Cheers,
Dr. A
does the angle between force and the radius vector is always constant for a particular torque....if it is so how can the bolt rotate in the same plane containing the force and the radius vector as its angle will be continuously changing
The torque formula is an instantaneous event. This isn't like work, where it is a cumulative quantity. Take the force, the radial coordinate, and the angle, all at the same time, and that gives you the corresponding torque at the same time. In an example in a non-calculus Physics where torque is applied through a rotation angle, they will usually give you a setup where the angle in the torque formula can remain constant. Both force and radius vector may rotate, but they both rotate the same, and the angle between them remains constant.
One example where it is NOT constant, is in a crankshaft of an automobile engine. At bottom-dead-center and top-dead-center, the piston cannot apply any torque to the crankshaft, because the force from the piston points directly through the center of the crankshaft, and the sine term is zero. It is much more effective after the shaft has rotated 90 degrees, and the connecting rod has better leverage on the shaft. This is part of the reason why gasoline engines need electric motors to assist with startup.
are you having lateral inversion like plane mirror?
Correct. Secrets here: www.learning.glass
Cheers,
Dr. A
I was wondering about direction of cross product. consider if we push the door in outward direction, with force perpendicular to the length of door. the force is in forth direction and moment arm is perpendicular to it, then if we use right hand rule than door should move upward!!! I am confused about this
Suppose the hinge is on the left side, and you open the door opens away from you. You push forward. The radius vector points to the right. The torque on the door is (by our convention), pointing upward along the axis of the hinge.
The direction of angular quantities is defined in the direction of the axis of rotation, and doesn't necessarily correspond to anything physical happening in that direction. Think of it as the direction that the motion *isn't* happening, because motion is happening in the other two directions, and there is no clear reason to choose either of them. It is an arbitrary convention that we define it with a right-hand rule. We could've just as easily defined it with a left-hand rule.
I know you take the mirror image to show the lightboard correctly, but it causes another ambiguity. You show your left hand while telling about the right-hand rule.
I always assumed torque was in the direction of motion, but I guess it isn't. So, wait, angular momentum is also perpendicular to both r and p, so is torque and angular momentum the same thing?
Torque and angular momentum are not the same thing, but both have a direction given by the right hand rule. Think of an object laying on your table. If the object is being twisted in the clockwise (CW) direction by a torque, then the direction of the torque is into the table. If the object is being twisted in the counter-clockwise (CCW) direction by a torque, then the direction of the torque is out of the table. This is the ole "Righty tighty lefty loosey" phrase that applies to screws. Turn it to the right (CW), it gets tighter because it is going into the table. Turn it to the left (CCW) , it gets looser because it's coming out of the table.
(Sidebar: this only works on normal right-handed screws. Very occasionally, you come across left-handed screws and everything is reversed.)
Angular momentum has the same rules for direction, but of course different units since angular momentum has to do with rotational velocity, not rotational force.
Hope this helps.
Cheers,
Dr. A
why to take r x F...why not Fxr...how u know wheather to take rxF or FxR???
It's just by convention. If instead of rxF you take Fxr you will get a torque in the opposite direction.
Good question.
Cheers,
Dr. A
What if you have your right hand amputated?
+xMinimalistic
You can use your left hand, but when you're done you need to add a minus sign. So your thumb will point in the opposite direction.
Cheers,
Dr. A
Mirror-you will then have his left hand amputated.
he just used his left hand
Alex,
Yep, I need to use my left hand for all "right-hand rule" demonstrations. And on top of that, I have to remember that vectors towards me (out of the page) are actually flipped (into the page). The right hand rule was the trickiest part of using the Learning Glass.
Cheers,
Dr. A
The door looks like a baseball bat...
How is it a door?
Sharon 92075,
My career as an artist is in jeopardy.
Thanks for the comment, and keep up with the physics!
You might also like my new website: www.universityphysics.education
Cheers,
Dr. A
Think of it as the base of the door or cross section. We are dealing with lines and directions so he has simplified an acual door. I must admit I was reminded of Homer's appraisal of Kirk Van Houten's sketch though ("That's a door?!!!") 😆