Hyperbolic Motion: SR Homework Solutions

Kiwithepike
Messages
16
Reaction score
0

Homework Statement


Consider a particle in one-dimensional so called hyperbolic motion
x(t)=\sqrt{b^{2}+t^{2}}
where b is a constant.

a) Find\gamma(t).
b) Find the proper time \tau(t). (assume that \tau=0 when t = 0
c) Find x and v_x as functions of the propertime \tau.
d) FInd the 4-velocity u^{\mu}.

The Attempt at a Solution



A) ok to begin I took the derivative of x(t) to get velocity. tuned out to be t(b^{2}+t^{2})^{-1/2}.
soo therefor \gamma(t) = \frac{\sqrt{b^{2}+t^{2}}}{\sqrt{1-\frac{t^{2}}{\sqrt{b^{2}+t^{2}}}}}

b) so now \tau(0) = \sqrt{t^{2}-(b^{2}+t^{2}}
\tau(0) = \sqrt{0^{2}-(b^{2}+t^{0}} = 0
\tau(0) = \sqrt{-b^{2}} = 0
so would b = 0?
this is where I'm getting lost.
c) x as a function of \tau would be \sqrt{t^{2}-\tau^{2}}=x?
where does v_x come in? would i solve v(t) for t^2?

d) I know the 4 vector for u^{\mu} is (u^0,u^1,u^2,u^3) and the roattional lorrentz for hyperbolic is
|t'| = |cosh\varphi -sinh\varphi |
|x'| |-sinh\varphi cosh\varphi |

where tanh\varphi=v
where cosh\varphi= \gamma

where do i go from here? Thanks for all the help.
 
Last edited:
Physics news on Phys.org
Kiwithepike said:
b) Find the proper time \tau(t). (assume that \tau=0 when t = 0

Try using ##d\tau^2 = dt^2 - dx^2##.
 
Thread 'Need help understanding this figure on energy levels'
This figure is from "Introduction to Quantum Mechanics" by Griffiths (3rd edition). It is available to download. It is from page 142. I am hoping the usual people on this site will give me a hand understanding what is going on in the figure. After the equation (4.50) it says "It is customary to introduce the principal quantum number, ##n##, which simply orders the allowed energies, starting with 1 for the ground state. (see the figure)" I still don't understand the figure :( Here is...
Thread 'Understanding how to "tack on" the time wiggle factor'
The last problem I posted on QM made it into advanced homework help, that is why I am putting it here. I am sorry for any hassle imposed on the moderators by myself. Part (a) is quite easy. We get $$\sigma_1 = 2\lambda, \mathbf{v}_1 = \begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix} \sigma_2 = \lambda, \mathbf{v}_2 = \begin{pmatrix} 1/\sqrt{2} \\ 1/\sqrt{2} \\ 0 \end{pmatrix} \sigma_3 = -\lambda, \mathbf{v}_3 = \begin{pmatrix} 1/\sqrt{2} \\ -1/\sqrt{2} \\ 0 \end{pmatrix} $$ There are two ways...
Back
Top