Kinematics: position, velocity, acceleration

Level UniversityDifficulty ★★★★★Application⌖ Open in the map

What is it?

Describing motion without its causes: velocity is the derivative of position, acceleration the derivative of velocity. Robots, drones, cameras and game characters all plan and track trajectories with these derivatives.

Formulas

v(t)=x˙(t),a(t)=x¨(t),x(t)=x0+∫0tv(s) dsv(t) = \dot x(t), \qquad a(t) = \ddot x(t), \qquad x(t) = x_0 + \int_0^t v(s)\,\dd s
x(t)=x0+(x1−x0)(10τ3−15τ4+6τ5),τ=t/Tx(t) = x_0 + (x_1 - x_0)\big(10\tau^3 - 15\tau^4 + 6\tau^5\big), \quad \tau = t/T
minimum-jerk point-to-point motion (zero velocity and acceleration at both ends)

Why does it matter?

Smooth trajectories (bounded velocity, acceleration and jerk) protect motors, passengers and camera footage.

The mathematics behind it

  • Derivative★★★★★fundamental

    Velocity is the derivative of position, acceleration the derivative of velocity.

  • Higher-order derivatives★★★★★fundamental

    Acceleration is the second derivative of position; Newton's law F=maF = ma is about it.

Where is it used?

Computing topics reachable from here, through the chain of ideas that leads to them:

What depends on it

This page has the essentials. A fuller treatment (intuition, formal definition, worked example) is on the way.

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