# Lorentz transform

mntb
derivating a from v (lorentz transform)
u is the velocity in the +x direction
u=(u-v)/(1-vu/c^2)
du? how do you du the right side of the eq?

## Answers and Replies

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mntb said:
derivating a from v (lorentz transform)
u is the velocity in the +x direction
u=(u-v)/(1-vu/c^2)
du? how do you du the right side of the eq?

What are you taking the derivative with respect to? Note that the u-time in the observed frame is not the same as the v-time in the reference frame. If you want your derivative to be Lorentz invariant you have to differentiate with respect to proper time.