B Magnitude vs. Size: Understanding the Difference

AI Thread Summary
Magnitude refers to the numerical value of a vector's strength, such as 9 Newtons, while size pertains to the physical representation of that vector, like a 4 cm line on paper. The discussion highlights that the scale used to represent the vector can vary, making the drawn size independent of the actual magnitude. Participants emphasize that in scientific contexts, the focus is typically on the vector's magnitude rather than its drawn size. The inconsistency in scale, such as using 4 cm to represent 9 N, is criticized for being arbitrary. Ultimately, understanding the distinction between magnitude and size is crucial for accurate representation in physics and engineering.
Bassel AbdulSabour
Messages
8
Reaction score
0
What's the difference between magnitude and size? I mean, how can I say that AB vector has a magnitude of 9 Newton, and its length is 4 cm.
 
Mathematics news on Phys.org
I can see a reason for them to be different. Suppose one draws ##\vec{AB}## 4 cm long and that should represent 9 N, then you have a scale of ##{9 \over 4} ## N/cm. Then AB has a size of 4 cm and a magnitude of 9 N.
 
Bassel AbdulSabour said:
What's the difference between magnitude and size? I mean, how can I say that AB vector has a magnitude of 9 Newton, and its length is 4 cm.
You are trying to distinguish between the magnitude of a vector and the size of its representation drawn on a piece of paper? In my lifetime I have never heard anyone refer to the "size" of a vector in such a manner. Scientists, engineers and mathematicians are normally concerned with the vector, not with its representation.
 
jbriggs444 said:
You are trying to distinguish between the magnitude of a vector and the size of its representation drawn on a piece of paper? In my lifetime I have never heard anyone refer to the "size" of a vector in such a manner. Scientists, engineers and mathematicians are normally concerned with the vector, not with its representation.
I agree completely. The fact that the vector is drawn as one 4 cm. in length is immaterial -- its magnitude is 9 Nt.
 
Last edited:
4cm = 9N is a horrible scale. Why not 1cm = 2N?
 

Thread 'Non-orthogonal bases'

Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
View full post »

Thread 'What Exactly is Dirac’s Delta Function? - Insight'

Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
View full post »

Similar threads

B Confusion about the angle between two vectors in a cross product
Replies
7
Views
3K
Vector Calculus in 1D: ± to Show Magnitude?
Replies
7
Views
2K
I What is the magnitude of a tensor?
Replies
9
Views
7K
B Why Do We Draw Dimensionless Unit Vectors in Diagrams?
Replies
16
Views
4K
I General equation for the magnitude of the difference vector
Replies
15
Views
2K
B Geometrical meaning of magnitude of vector product
Replies
9
Views
2K
Velocity vectors; arrow length
Replies
3
Views
874
I Modern vs Euclid's definition of equivalent ratios
Replies
4
Views
2K
MHB Understanding How to Solve Vector Magnitudes and Angles
Replies
1
Views
2K
I What is the role of geometry and dimensional operations?
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top