Statics of Rigid Bodies Topic

Finding Center of Gravity

Concept 3 demos

Irregularly shaped wooden board suspended from a horizontal rod, with several red chalk lines drawn across it intersecting near the center; a yellow surveyor's chalk line hangs as a plumb bob

Center of Gravity Board

Experimentally locates the center of gravity of an irregular board by hanging it from different points and marking plumb lines. Students see that the CG must lie along every vertical …

Four-panel sequence: person in red sweater holding a uniform meter stick horizontally, sliding hands inward from the ends until they meet at the center

Center of Meter Stick

Sliding hands along a meter stick always converge at the center of mass, regardless of starting position. Comparing a uniform stick (hands meet at 50 cm) with a weighted stick …

Wooden disk with concentric orange ring centered on the geometric center

Loaded Disk

Demonstrates that rotation appears smooth when viewed about the center of mass but wobbles when viewed about the geometric center. Students see directly why center of mass is the natural …

Exceeding Center of Gravity

Concept 4 demos

Worn metal Leaning Tower of Pisa model made of stacked cylindrical segments of decreasing diameter, leaning noticeably, with a separate bell-shaped top piece sitting beside it on a green surface

Leaning Tower

A Leaning Tower of Pisa model balances stably without its top piece. Adding the top shifts the center of gravity beyond the base, and the tower topples — showing that …

Seven wooden blocks stacked in a staircase overhang pattern on a bench edge, each offset from the one below, with the top block extending well beyond the base, photographed against a chalkboard

Overhanging Block

Demonstrates the Tower of Lire: marked blocks are stacked so the top block extends completely beyond the table edge while maintaining static equilibrium. Students see that the maximum overhang follows …

Front and back views of the articulated wooden figure in a standing pose with one arm raised and one hand on hip

Human Center of Gravity

Demonstrates how center-of-gravity position relative to the base of support determines balance. Students see that a person (or articulated figure) standing with heels against a wall cannot bend forward to …

Stable, Unstable, and Neutral Equilibrium

Concept 4 demos

Three plastic funnels demonstrating equilibrium types: upright on rim (stable), inverted on spout (unstable), and lying on side (neutral)

Equilibrium Cones

Funnels placed in three orientations demonstrate stable, unstable, and neutral equilibrium. Students see how center-of-mass position relative to the support determines the equilibrium type and the system's response to perturbation.

Stable and Unstable Acrobat

Demonstrates stable, unstable, and neutral equilibrium using objects balanced on rings of different radii. Students see that an object on a curved surface is stable when its center of mass …

Wooden figure with round white head standing on a black pedestal; long curved wire arms arc downward on both sides with weights at the tips, lowering the center of mass below the feet

Balancing Figure

Demonstrates stable equilibrium by showing that when the center of mass is below the pivot point, the system returns to equilibrium after displacement. The figure's long weighted arms lower its …

Resolution of Forces

Concept 5 demos

Basswood strip supported at each end on wooden blocks, bending visibly under a brass mass with hook placed at center

Normal Force

A flexible basswood strip bends visibly under load, showing that normal forces arise from elastic deformation of the supporting material. Heavier masses produce greater deflection, making the connection between deformation …

Lecture bench with pulley clamps at each end, wheeled cart with stacked blue lead bricks in center, white ropes running from the cart and bricks over the pulleys

Tricky Tension Problem

A cart with lead bricks stays in equilibrium with 3 kg hanging from each side, but slides when 6 kg hangs from one side and the other rope is anchored. …

Two ring stands on a bench with a horizontal rod across the top; pink fluorescent string in a V-shape supports a brass mass at center; a yellow-green string runs over a pulley to a large circular dial spring scale reading about 18 N, with a hand pulling down

Perpendicular Forces

A mass hangs from a string while a spring scale attempts to pull the string horizontal. Students see that no matter how hard they pull, the string cannot be made …

Static Torque

Concept 7 demos

Hand gripping wooden cylindrical handle with thin metal rod extending left; a brass 1 kg mass hangs from a notch near the middle of the rod

Torque Bar

A volunteer holds a bar by its handle and tries to keep it horizontal while a 1 kg mass is hung from progressively farther notches. Students feel (or watch someone …

Seven wrenches arranged diagonally from smallest to largest on gray surface, including small combination wrenches and progressively larger adjustable wrenches up to a 24-inch model

Wrenches

A set of wrenches ranging from tiny to a 24-inch behemoth illustrates how lever arm length affects torque . The dramatic size progression makes mechanical advantage viscerally obvious.

Red-and-yellow checkered meter stick balanced on a black pivot stand, with a brass mass hanging from a screw clamp on the left and a larger black cylindrical mass on the right, mass set visible behind the pivot

Meter Stick on Support

Hanging different masses at different lever arm positions on a pivoted meter stick demonstrates torque balance. Students verify that at equilibrium and predict where to place masses to achieve balance.