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Concepts Of Physics MCQ Edition [Volume 2]PhysicsThe Special Theory of Relativity

Determine the speed at which the volume of an object shrinks to half of its rest value.

Options

  1. Ac 2
  2. B3 ,c 4
  3. Cc 2
  4. D3 ,c 2

Correct answer

D. 3 ,c 2

Step-by-step solution

Let the rest volume of the object be V₀ = L_x L_y L_z . When the object moves with a speed v along the x-axis, its length in the direction of motion contracts due to length contraction, while the perpendicular dimensions remain unchanged. The new length is L'_x = L_x 1 - v^2 c^2 . The new volume is V = L'_x L_y L_z = V₀ 1 - v^2 c^2 . Given that the volume shrinks to half of its rest value, V = V₀ 2 . V₀ 2 = V₀ 1 - v^2 c^2 1 4 = 1 - v^2 c^2 v^2 c^2 = 3 4 v = 3 ,c 2

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