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Why the velocity is relative but acceleration is absolute? |
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Answer» y is defined as CHANGE of DISPLACEMENT per unit time. Usually velocity is measured with respect to an inertial frame of reference, ie., a coordinate system which does not move. So we choose the distant star in the universe which is stationary as the reference, and measure all velocities WRT to it. In our world we measure velocities wrt objects that are stationary on Earth. So velocity is measured as a relative quantity.Acceleration is defined as change of velocity per unit time. That is a = (v - u) / Δtlet v and u be measured relative to a frame of velocity v₀. Then the absolute velocities of an OBJECT at two points of time are: v + v₀ and u + v₀ respectively. Then acceleration a = [v + v₀ - u - v₀ ] / Δt a = (v - u) / ΔtThus acceleration is absolute, whether we TAKE absolute velocities or relative velocities of a particle to compute it. |
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