# Mechanics Demos

#### Statics

Blackboard Mechanics
Promotes understanding of basic concepts of mechanics including equilibrium, resolution, and composition of forces, levers, inclined planes, pulleys, friction, etc.

Inertia Demo
Pulling down with either an even force or with a jerk causes one of two different strings to break due to the inertia of the mass.

Center of Mass
Three demonstrations are available: Bear on a String, Balancing Bird, and Forks and Cork.

Finding the Center of Mass for Irregularly Shaped Objects
This blackboard demonstration uses a plumb line to find the center of mass for either a cardboard “amoeba” or a plastic polygon.

#### Kinematics and Dynamics

Pulley System Dynamics:

Cartesian Coordinate System
Three perpendicular meter sticks are attached to model the Cartesian coordinate system.

Coin and Feather
This demonstration reproduces Galileo’s thought experiment of dropping a coin and feather simultaneously in an evacuated cylinder.

Dynamic Systems — Frictionless Track
Two setups are available: an air track with gliders of various masses and a grooved track with low-friction carts. These can be used to demonstrate a variety of concepts including velocity, acceleration, conservation of momentum, elastic and inelastic collisions, etc.

Composition of Motions
The apparatus simultaneously drops one ball and launches a second ball horizontally to demonstrate the independence of horizontal and vertical motion.

Monkey and Hunter Demo
A blow tube is aimed at a monkey suspended from a “tree”. As a ball is shot from the tube, the monkey drops from the tree. If the tube is pointing directly at the suspended monkey, the monkey “catches” the ball.

Ball Rolling Down Inclined Plane
Galileo’s experiment showing constant acceleration.

Friction – Static and Kinetic
Demonstrates static and kinetic friction using weights and different textured surfaces.

Ratchet Pulley
Demonstrates a simple ratchet mechanism.

Fan Cars
Demonstrates how electric potential energy can be transformed into mechanical energy.

Cycloid Ramp
A series of ramps demonstrating the fastest path between two points.

#### Conservation of Momentum / Conservation of Energy

Pendulums:

• Pendulum and Peg
Pendulum rises to its original height despite obstructing peg.
• Pendulum and Ball on Track
Shows two balls of equal mass released from the same height (one on a pendulum and one on a track) to show the difference between translational and rotational motion.
• Coupled Pendulum
Two pendulums connected by a soft spring.
• Bowling Ball Pendulum
This is a popular demonstration with a heavy ball suspended from the ceiling.
• Double Physical Pendulum
Similar to the pendulum in ISB, this pendulum is used to show chaotic motion.
• Ballistic Pendulum
A ball is ejected from a spring loaded “gun” and collides inelastically with a bob, demonstrating conservation of momentum.

Momentum Transfer
Two pendulums with elastic and inelastic bobs are released one after another. Colliding with a wooden board, they produce different effects.

Stacked Rubber Balls
A basketball ball and a small ball are stacked and dropped simultaneously. The result is surprising for students.

Conservation of Momentum — “Medicine” Ball, Sandbags, and Carts
Student volunteers sit on skateboard “carts” with sandbags and toss them off to move backwards.

Swinging Wonders
An excellent example of energy conservation and elastic collisions.

Loop Track and Ball
Ball does a “loop-dee-loop” as it rolls along a track. Demonstrates conservation of energy and allows the instructor to introduce an interesting problem.

Potential Well Track
Introduces a two-level system of potential energy.

Wave-Shaped Track
Designed to demonstrate energy transformation, oscillations, frictionless motion, roller coaster, etc.

#### Rotational Motion

Gyroscopes:

Centripetal Force Apparatus
Allows measuring the centripetal force produced by a swinging ball.

Rotating Stool, High Moment-of-Inertia Bicycle Wheel, and Dumbbells
This is an excellent series of demonstrations to show conservation of angular momentum.

Rotating Candle Apparatus
Shows the effect of the centripetal force on gases.

Swinging Coffee Cup
Liquid remains inside the cup throughout the rotational cycle.

Inclined Plane with Cylinders
Various cylinders rolling down an incline plane behave differently.

Large Gravity Funnel
Billiard balls roll around a large funnel as they are affected by a strong gravitational field, found near a black hole.

Rattleback
Wooden half peanut shape that only spins in one direction. If spun the incorrect direction it will stop and correct its direction.