Solvequill Blog · physics · 4 min read · 2 views

Free-body diagrams that actually do work

A practical way to draw force diagrams that lead directly to equations instead of decorative arrows.

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A useful force diagram is not a drawing of the object. It is a drawing of the interactions acting on the object.

The main idea

Choose one object, replace it with a dot or box, then draw only external forces: weight, normal, tension, friction, applied force.

A short example

For a block on a table pulled right, the vertical forces are and ; the horizontal forces are the pull and friction.

Check while you solve

  • Pick the object before drawing arrows.
  • Do not draw velocity as a force.
  • Split tilted forces into components only after the diagram is clear.

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