According to the beginning of the 20th century, the famous physicist Albert Einstein's theory of special relativity builds qualities for the movement of objects with increasing speed. The quality of the relationship between the velocity of the object is , Where m0 is the mass of the stationary object, m is the mass velocity of the object when v, c is the speed of light in vacuum. Visible when v << c, m ≈ m0; as v approaches c, m approaches infinity. Therefore, when the speed of the object is much less than the speed of light in vacuum, classical mechanics is fully applicable; When an object approaches the speed of light, classical mechanics does not apply. (2) the velocity superposition principle in classical mechanics is no longer valid. Let the speed of the water in the river relative to the shore be, the speed of the boat relative to the water, so in classical mechanics, the speed of the boat relative to the shore times (vector