Locate weights and moment arms
Use the measured balance mark of a nonuniform stick and retain a uniform beam’s own weight. Distinguish a load coordinate from its distance to the support.
AP Physics 1 · Unit 5 · Rotation
Rotational Equilibrium Practice Problems
Use force balance and moment balance together. Find a forearm’s muscle force, infer a meter stick’s mass, follow a beam toward tipping, resolve three rope tensions, and calculate the cable and hinge forces supporting a sign.
12 questions6 conceptual · 6 calculation
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What you’ll practice
Balance forces and moments about a useful reference
Find support and cable forces
Resolve muscle, cable, and hinge forces using the stated angle reference. Use both horizontal and vertical force equations after a moment equation eliminates convenient unknowns.
Test equilibrium and its limits
Distinguish steady rotation from static equilibrium, change a moment reference without moving the support, and identify tipping when a pushing support unloads.
A question from this set
Zero net torque and angular motion
A rigid wheel about a fixed axle has zero net torque. Which motion is consistent with rotational equilibrium?
Try it in the practice setKey ideas
Zero net force and zero net torque are separate conditions
A reference point simplifies an equation
Taking moments about a support removes that support force from the moment equation. It does not remove the force from the physical system or from other equilibrium equations.
Different supports permit different force directions
A resting contact can push upward but cannot hold a beam down. A hinge or joint can exert signed components in either direction, and a taut rope pulls along its length. These distinctions determine which equilibrium solutions are possible.
See the physics
Watch a contact force vanish at the tipping limit
After attempting the questions, inspect measured force and moment sums. The moving worker load advances along a free beam on two supports; the recorded unloading event identifies the tipping position. Other trials compare cable angles, support references, and alternative load placements.
Use a hint for a starting point or open a worked solution to follow the reasoning. Your progress saves in this browser, so you can return to unfinished questions.
Ready for rotational equilibrium?
Begin with a conceptual question, then work through the calculations.