- #1

**[SOLVED] Force using relativistic momentum**

I have an example problem in a textbook I'm reading:

"Find the acceleration of a particle of mass m and velocity v when it is acted upon by the constant force F, where F is parallel to v.

then it proceeds to show the solution:

[tex]F = \frac{d}{dt}(\gamma mv) = m\frac{d}{dt}(\frac{v}{\sqrt{1-v^{2}/c^{2}}})[/tex]

I get all that so far. The next step is where it loses me:

[tex]= m[\frac{1}{\sqrt{1-v^{2}/c^{2}}} + \frac{v^{2}/c^{2}}{(1-v^{2}/c^{2})^{3/2}}] \frac{dv}{dt}[/tex]

so I don't know how they got there... and then the next step confuses me also. They go from above to here:

[tex]= \frac{ma}{(1-v^{2}/c^{2})^{3/2}}[/tex]

and then of course there a few more steps after that one, but I can get those, I'm just confused about those two steps. Please help clarify it for me, thank you.