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How is acceleration defined using the second derivative of displacement with respect to time?

Acceleration is defined as the second derivative of the position (or displacement) function s(t)s(t) with respect to time tt. It represents the rate of change of velocity, where velocity itself is the first derivative of displacement.

Conditions

  • Motion occurs along a fixed line with a chosen coordinate direction.
  • The position function s(t)s(t) is twice differentiable with respect to time.

Reasoning, step by step

  1. Define displacement as a function of time, s(t)s(t).
  2. Compute the first derivative dsdt\frac{ds}{dt} to obtain velocity v(t)v(t).
  3. Compute the derivative of velocity, which is the second derivative of displacement d2sdt2\frac{d^2s}{dt^2}.
  4. Identify this quantity as acceleration a(t)a(t).

Example

In the car animation, the graph of s(t)s(t) is shown. Its slope gives velocity, and the slope of the velocity graph (which is the curvature of the position graph) gives acceleration, labeled as d2sdt2\frac{d^2s}{dt^2}.

Common misconceptions

  • Confusing acceleration with velocity.
  • Thinking acceleration is the derivative of position directly without passing through velocity.

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