In the earth's reference frame, a tree is at the origin and a pole is at x = 30 km. Lightning strikes both the tree and the pole at t = 20 μs. The lightning strikes are observed by a rocket traveling in the x-direction at 0.70 c.

What are the spacetime coordinates x? tree, x? pole for these two events in the rocket's reference frame?

What are the spacetime coordinates t? tree, t? pole for these two events in the rocket's reference frame?

Respuesta :

Answer:

[tex]x'_t=-5880\ m[/tex]

[tex]x'_p=-1680\ m[/tex]

[tex]t'_t=28\ \mu s[/tex]

[tex]t'_p=18.2\ \mu s[/tex]

Explanation:

Given:

  • position of tree on the earth, [tex]x_t= 0[/tex]
  • position of pole on the earth, [tex]x_p=30\ km[/tex]
  • time at which the event occurs, [tex]t=20\ \mu s[/tex]
  • velocity of observer in the rocket with respect to the earth, [tex]v=0.7c[/tex]

Now the space coordinate x for tree and pole as observed from the rocket:

[tex]x'_t=\gamma (x_t-v.t)[/tex]

where:

[tex](\rm lorentz\ factor)\ \gamma= \frac{1}{\sqrt{1-\frac{v^2}{c^2} } } = \frac{1}{\sqrt{1-\frac{(0.7c)^2}{c^2} } }=1.4[/tex]

[tex]x'_t=1.4\times (0-(0.7\times 3\times 10^8)\times (20\times 10^{-6}))[/tex]

[tex]x'_t=-5880\ m[/tex]

and

[tex]x'_p=\gamma (x_p-v.t)[/tex]

[tex]x'_p=1.4\times (3000-(0.7\times 3\times 10^8)\times (20\times 10^{-6}))[/tex]

[tex]x'_p=-1680\ m[/tex]

Now, time coordinates:

[tex]t'_t=\gamma (t-\frac{v.x_t}{c^2} )[/tex]

[tex]t'_t=1.4\times (20\times 10^{-6}-\frac{0.7c\times 0}{c^2} )[/tex]

[tex]t'_t=28\ \mu s[/tex]

and

[tex]t'_p=\gamma (t-\frac{v.x_p}{c^2} )[/tex]

[tex]t'_p=1.4\times (20\times 10^{-6}-\frac{0.7c\times 3000}{c^2} )[/tex]

[tex]t'_p=18.2\ \mu s[/tex]