# Instantaneous acceleration in non uniform circular motion

How is instantaneous acceleration different from tangential acceleration in a non uniform circular motion?

We know that instantaneous acceleration is tangent to a point at any given time and so is the tangential acceleration. What is there difference?

• in constant circular motion, you only have a radial component of acceleration - always moving towards the center, never getting there. Tangential acceleration is along the tangent so at right angles to the radial vector. These are not the same thing. – Floris Jan 14 '15 at 5:18
• @Floris I was asking the difference between tangential and instantaneous acceleration in a circular motion(non uniform). Not between radial and tangential acceleration. – pcforgeek Jan 14 '15 at 5:38
• Instantaneous acceleration is the vector sum of tangential acceleration and radial acceleration (at a certain time). – Mark Fantini Jan 14 '15 at 6:23
• Why would instantaneous acceleration be tangent? Instantaneous should be the value of acceleration at any one point in time (distinct from average acceleration). The time derivative of velocity evaluated at one point in time would be the instantaneous acceleration. – BowlOfRed Jan 14 '15 at 6:23
• Doesn't instantaneous acceleration just mean acceleration as opposed to average acceleration? Are you actually asking how the radial acceleration differs from the tangential acceleration? If so I can't see what would be meant by a difference. Perhaps you could clarify your question to indicate what difference you have in mind. – John Rennie Jan 14 '15 at 10:09