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📘 Start by isolating one object

Pick one body. List every external push or pull before you draw a single arrow.

3
lessons
~15 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. Build the diagramIsolate one body and draw labeled force vectors from physical interactions.Choose the system boundary first; every arrow starts on the body and points in the force direction.
  2. Forces on surfacesSeparate normal force and friction and choose helpful axes.Normal is perpendicular to the surface; friction opposes sliding; axes are a bookkeeping choice.
  3. Solve with NewtonAvoid false forces, draw separate diagrams for multiple bodies, and sum components.Net force is the vector sum of interactions; ΣF = ma component by component.

Questions this course answers

What should you do first when drawing a free-body diagram?

The system boundary determines which external interactions belong in the diagram.

Which force can act without physical contact near Earth?

Gravity is a field interaction; the other listed forces require contact or a connector.

How is the normal force directed relative to a surface?

The normal reaction is perpendicular to the contacting surface.

If two objects are analyzed separately, where does an action-reaction pair appear?

Newton's third-law forces act on different bodies, so each belongs on its own body's diagram.

What does the sum of forces in one axis equal?

Newton's second law gives sum of forces in an axis as m times acceleration in that axis.

Grounded in trusted sources

  • [object Object]
  • [object Object]
  • [object Object]
  • [object Object]

Every Wunder lesson is built from real, reputable sources — never invented.

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