Hyperbolic Motion: SR Homework Solutions

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SUMMARY

The discussion focuses on solving a hyperbolic motion problem in special relativity, specifically analyzing the motion of a particle described by the equation x(t) = √(b² + t²). Key solutions include the derivation of the Lorentz factor γ(t) as γ(t) = √(b² + t²) / √(1 - t²/(b² + t²)), and the proper time τ(t) which is evaluated at τ(0) = 0. The participants also explore the relationships between position x, velocity v_x, and the four-velocity u^{μ}, utilizing the Lorentz transformation matrix for hyperbolic motion.

PREREQUISITES
  • Understanding of special relativity concepts, particularly hyperbolic motion.
  • Familiarity with calculus, specifically differentiation for velocity calculations.
  • Knowledge of Lorentz transformations and four-vectors.
  • Ability to manipulate square roots and algebraic expressions in physics contexts.
NEXT STEPS
  • Study the derivation of the Lorentz factor in various motion scenarios.
  • Learn how to compute proper time in different relativistic contexts.
  • Explore the application of four-velocity in special relativity problems.
  • Investigate the implications of hyperbolic motion on particle dynamics in physics.
USEFUL FOR

Students and educators in physics, particularly those studying special relativity and hyperbolic motion, as well as anyone involved in solving advanced mechanics problems.

Kiwithepike
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Homework Statement


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

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

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[itex]^{2}[/itex]+t[itex]^{2}[/itex])[itex]^{-1/2}[/itex].
soo therefor [itex]\gamma[/itex](t) = [itex]\frac{[itex]\sqrt{b^{2}+t^{2}}[/itex]}{[itex]\sqrt{1-\frac{t^{2}}{\sqrt{b^{2}+t^{2}}}}[/itex]}[/itex]

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

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

where tanh[itex]\varphi[/itex]=v
where cosh[itex]\varphi[/itex]= [itex]\gamma[/itex]

where do i go from here? Thanks for all the help.
 
Last edited:
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Kiwithepike said:
b) Find the proper time [itex]\tau[/itex](t). (assume that [itex]\tau[/itex]=0 when t = 0

Try using ##d\tau^2 = dt^2 - dx^2##.
 

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