An unstable particle is created in the upper atmosphere from a cosmic ray and travels straight down toward the surface of the earth with a speed of 0.99537 c relative to the earth. A scientist at rest on the earth's surface measures that the particle is created at an altitude of 40.0 km .

QUESTION 1: As measured by the scientist, how much time does it take the particle to travel the 40.0 km to the surface of the earth?
QUESTION 2: Use the length-contraction formula to calculate the distance from where the particle is created to the surfaceof the earth as measured in the particle's frame.
QUESTION 3: In the particle's frame, how much time does it take the particle to travel from where it is created to the surface of the earth?

Respuesta :

Answer:

Q1)  Time taking by particle to travel the 40 km wrt. earth = [tex]1.34\times10^{-6}[/tex] sec.

Q2) The distance traveled by particle where the particle created to surface of earth wrt. particle's frame = 3.84 km.

Q3) The time taking by particle to travel from where it is created to the surface of the earth = [tex]1.285\times10^{-5}[/tex] sec.

Explanation:

Given :

Speed of particle wrt. earth [tex]v=0.99537c[/tex]

Distance between where particle is created and earth surface = 40 km

we know that,

⇒       [tex]v = \frac{x}{t}[/tex]

Where [tex]x = 40\times10^{3} m[/tex], [tex]v = 0.99537c[/tex], we know speed of light [tex]c = 3 \times10^{8}[/tex]

∴      [tex]t = \frac{x}{v}[/tex]

         [tex]= \frac{40 \times10^{3} }{0.99537\times3\times10^{8} }[/tex]

      [tex]t = 1.34\times10^{-6} sec[/tex]

∴ Thus, time taking by particle to travel the 40 km wrt. earth [tex]t = 1.34\times10^{-6} sec[/tex]

According to the lorentz transformation,

⇒    [tex]l = l_{o} \sqrt{1-\frac{v^2}{c^2} }[/tex]

Where [tex]l =[/tex] improper length, [tex]l_{o} =[/tex]proper length (distance measured wrt. rest frame) = 40 km

     [tex]l = 40 \sqrt{1-\frac{v^2}{c^2 }[/tex]

     [tex]l = 40 \times 0.096[/tex]

     [tex]l = 3.84[/tex] km

∴ Thus, the distance traveled by particle where the particle created to surface of earth wrt. particle's frame = 3.84 km.

According to the time dilation,

   [tex]\Delta t = \frac{\Delta t_{o} }{\sqrt{1-\frac{v^2}{c^2} } }[/tex]

Where [tex]\Delta t =[/tex] improper time (wrt. earth frame time) [tex]=1.34\times10^{-6} sec[/tex] ,  [tex]\Delta t _{o} =[/tex] proper time (wrt. particle frame).

 [tex]1.34\times10^{-6} = \frac{ \Delta t_{o}}{0.096}[/tex]

 [tex]\Delta t_{o} = 1.285 \times10^{-5} sec[/tex]

Thus, the time taking by particle to travel from where it is created to the surface of the earth [tex]= 1.285 \times10^{-5} sec[/tex].

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