This is what we refer to as a "convention." A convention is something chosen not out of any kind of real physical law, but because of either arbitrary choice or cultural factors. Another example of a convention is how we demarcate time. Why divide the day into 24 hours, each 60 minutes long, each 60 seconds long? That particular convention history going all the way back to ancient Babylon, but it's an example of something that was just chosen and then stuck around. Now, back to the moment. Counterclockwise moments are positive because engineering comes out of physics, and physics tends to use counterclockwise as positive for anything involving rotation. It gets interesting when you consider 3D coordinate systems. The way cross-products and other 3D vector operations work, there are really only two types of systems you can use that are internally consistent. You can use either a "right-handed system" or a "left-handed system." See here: en.wikipedia.org/wiki/Cartesian_coordinate_system#Orientation_and_handedness So the actual makeup of reality, physics, mathematics, etc, does dictate that we use either a left-handed or right-handed coordinate system. These are the only two ways to build a consistent x-y-z coordinate system. As for why we settled on right handed? Likely this is entirely cultural. Rationally, there is no reason to prefer a right-handed system. However, humans are humans. When we had to choose between left or right handed systems, predominant cultural forces took over. About 10% of humans are born left handed. If history teaches us anything, it's that human societies will always find a reason to take some insignificant difference between people and magnify it, stigmatize it, and use it as a means of dividing people. Taboos against left-handed people have existed all over the world and for all of history, and there are many places around the world where such stigma is still common. Rationally, looking down on someone for which hand they have dominant is one of the most patently absurd things we could possibly do, yet history shows that we are often anything but rational beings. Anyway, sorry for the long description, but this is one of those areas where engineering, mathematics, history, and sociology are all intricately woven and inseparable from one another. In summary, it could explained like this: 1. 90% of humans are born left handed. 2. Societies throughout history has used (1) as a reason for stigma against left-handed people and left-handedness in general. 3. Mathematicians discovered 3D coordinate systems and realized they had to be either right or left handed. They chose right-handed due to (2). 4. When physicists and engineers started working with the concept of moments, they define counterclockwise as positive due to using the right-handed coordinate system from (3).
Tanya can you recommend a good STRENGTH OF MATERIALS and STRUCTURAL ANALYSIS books. tnx
Hibbeler is pretty good for strength of materials. Hibbeler is also has a structural analysis book, but I prefer Kassimali.
tnx
Hi my name is Gowtham from India why clockwise moment is positive and anti clockwise is negative
This is what we refer to as a "convention." A convention is something chosen not out of any kind of real physical law, but because of either arbitrary choice or cultural factors. Another example of a convention is how we demarcate time. Why divide the day into 24 hours, each 60 minutes long, each 60 seconds long? That particular convention history going all the way back to ancient Babylon, but it's an example of something that was just chosen and then stuck around.
Now, back to the moment. Counterclockwise moments are positive because engineering comes out of physics, and physics tends to use counterclockwise as positive for anything involving rotation. It gets interesting when you consider 3D coordinate systems. The way cross-products and other 3D vector operations work, there are really only two types of systems you can use that are internally consistent. You can use either a "right-handed system" or a "left-handed system." See here:
en.wikipedia.org/wiki/Cartesian_coordinate_system#Orientation_and_handedness
So the actual makeup of reality, physics, mathematics, etc, does dictate that we use either a left-handed or right-handed coordinate system. These are the only two ways to build a consistent x-y-z coordinate system. As for why we settled on right handed? Likely this is entirely cultural. Rationally, there is no reason to prefer a right-handed system. However, humans are humans. When we had to choose between left or right handed systems, predominant cultural forces took over.
About 10% of humans are born left handed. If history teaches us anything, it's that human societies will always find a reason to take some insignificant difference between people and magnify it, stigmatize it, and use it as a means of dividing people. Taboos against left-handed people have existed all over the world and for all of history, and there are many places around the world where such stigma is still common. Rationally, looking down on someone for which hand they have dominant is one of the most patently absurd things we could possibly do, yet history shows that we are often anything but rational beings.
Anyway, sorry for the long description, but this is one of those areas where engineering, mathematics, history, and sociology are all intricately woven and inseparable from one another. In summary, it could explained like this:
1. 90% of humans are born left handed.
2. Societies throughout history has used (1) as a reason for stigma against left-handed people and left-handedness in general.
3. Mathematicians discovered 3D coordinate systems and realized they had to be either right or left handed. They chose right-handed due to (2).
4. When physicists and engineers started working with the concept of moments, they define counterclockwise as positive due to using the right-handed coordinate system from (3).
Same I had been ask to my professor they tell they have no idea so what will be the actual reason