# Magnitude and Size

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
Homework Helper
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
Homework Helper
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
Mentor
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:
CWatters