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relativistic mechanics[‚rel·ə·tə′vis·tik mi′kan·iks]
the branch of theoretical physics that considers the classical laws of motion of bodies or particles at rates of motion ν comparable with the speed of light. Relativistic mechanics is based on the theory of relativity. The basic equations of relativistic mechanics—the relativistic generalization of Newton’s second law and the relativistic law of conservation of energy-momentum—satisfy the requirements of Einstein’s relativity principle. In particular, it follows from these equations that the speed of material objects cannot exceed c, the speed of light in a vacuum. When ν ≪ c, relativistic mechanics reduces to classical Newtonian mechanics.