- #1
JabberWalkie
- 16
- 0
4-velocity --> 4-acceleration?
Hey all, my first post here.
Now, I am trying to derive the 4-acceleration from the 4-velocity by explicitly calculating du/d(tau). So from Hartle we have
u=( gamma, gamma*v)
where gamma=1/Sqrt(1-v^2)
and v is the 3 velocity, taking c=1
So then,
du/d(tau)=( d(gamma)/d(tau), d(gamma*v)/d(tau) )
from the book we have
du/d(tau)=(gamma*(a dot v), gamma*a)
so then we should have
d(gamma)/d(tau)=gamma*(a dot v)
but when i calculate d(gamma)/d(tau) i get...ok I am going to show all my steps so people can know what I've done...
d(gamma)/d(tau)=[d(gamma)/dv)]*[dv/dt]*[dt/d(tau)]
=[d(1/(1-v^2)^(1/2))/dv]*[a][gamma]
=[(-1/2)(-2*(v)/(1-v^2)^(3/2)]*[a]*[gamma]
=[ va/(1-v^2)^(3/2)*[1/gamma]
=v*a*gamma^4 != v*a*gamma
does anyone know what's going wrong or what I am doing wrong??
Any help would be appreciated, Thanks in advance.
Hey all, my first post here.
Now, I am trying to derive the 4-acceleration from the 4-velocity by explicitly calculating du/d(tau). So from Hartle we have
u=( gamma, gamma*v)
where gamma=1/Sqrt(1-v^2)
and v is the 3 velocity, taking c=1
So then,
du/d(tau)=( d(gamma)/d(tau), d(gamma*v)/d(tau) )
from the book we have
du/d(tau)=(gamma*(a dot v), gamma*a)
so then we should have
d(gamma)/d(tau)=gamma*(a dot v)
but when i calculate d(gamma)/d(tau) i get...ok I am going to show all my steps so people can know what I've done...
d(gamma)/d(tau)=[d(gamma)/dv)]*[dv/dt]*[dt/d(tau)]
=[d(1/(1-v^2)^(1/2))/dv]*[a][gamma]
=[(-1/2)(-2*(v)/(1-v^2)^(3/2)]*[a]*[gamma]
=[ va/(1-v^2)^(3/2)*[1/gamma]
=v*a*gamma^4 != v*a*gamma
does anyone know what's going wrong or what I am doing wrong??
Any help would be appreciated, Thanks in advance.