When the speed of a rod travelling parallel to its length at a relativistic speed is doubled,

Step-by-step solution

The relativistic mass m of an object moving with velocity v is given by: m = m₀ 1 - v^2 c^2 The relativistic length L of an object moving with velocity v parallel to its length is given by: L = L₀ 1 - v^2 c^2 When the speed v is doubled to 2v , the term v^2 c^2 increases to 4v^2 c^2 . Consequently, the factor 1 - v^2 c^2 decreases. As the denominator in the mass expression decreases, the relativistic mass m increases. As the factor in the length expression decreases, the relativistic length L decreases. Since the d