SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/eng-pivot-any-point

When solving a static equilibrium problem, where are you allowed to sum moments?

About any point you choose; a smart choice just makes the algebra easier.

Start playing free

  1. Only at the center of mass
  2. Only at an actual hinge or support
  3. About any point you choose ✔

Why: If a body is in equilibrium, the net moment is zero about every point. Engineers pick a point where unknown forces act, so those unknowns drop out of the equation.

Huh, didn't know that: Different pivot choices for the same problem must give the same final answers, which is a handy self-check.

The dad joke
I'm very flexible in statics. I'll pivot anywhere you like.
Like this card?
Play the game

References

Answer: About any point you choose. If a body is in equilibrium, the net moment is zero about every point. Engineers pick a point where unknown forces act, so those unknowns drop out of the equation.

  1. OpenStax University Physics Volume 1: 12.1 Conditions for Static Equilibrium openstax.org/books/university-physics-volume-1/pages/12-1-conditions-for-static-equilibrium
    we are free to choose any point as the origin of the reference frame.
    Checked 2026-10-11.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

EngineeringFor an object at rest, Newton's second law F = ma becomes what?EngineeringA force's line of action passes right through the pivot. What moment does it make about that pivot?EngineeringTorque is force times lever arm. Which SI unit is correct for torque?

That's stuff everyone should know.