Magnitude vs. Size: Understanding the Difference

[Bassel AbdulSabour]

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.

 

[verty]

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.

 

[jbriggs444]

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.

 

[Mark44]

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.

 

[CWatters]

4cm = 9N is a horrible scale. Why not 1cm = 2N?