What it shows:

A straightforward demonstration of Newton's 3rd law, that forces are interactions and thus come in pairs.

How it works:

Two people, each sitting (cross-legged) on their own board, position themselves in the center of the track facing each other. Upon pushing against each other with their hands, they glide apart down the length of the track. Repeat this with one person turned around — the other person pushes on his/her back instead of pushing against each other with their hands. The ensuing motion down the track is exactly the same as before.

Falling in an evacuated tube at the same rate.

What it shows:

In the absence of air resistance all bodies, regardless of size or weight, fall with the same acceleration at the same point above the Earth. Here a feather and a dime (see Comments) fall under the influence of gravity in an environment where there is no air to mess things up.

...

The tension force in a rope grows exponentially with the number of turns the rope makes around a pole.

... Read more about Rope Friction Around Pole

Prediction of motion of masses in a more complex pulley/mass assembly.

What it shows:  This compund Atwood's Machine demonstrates an old and interesting problem. The two small weights on the right side are not...

Combinations of weights suspended over pulley to show that asymmetry causes acceleration.

Image on the left, of a lightweight plastic pulley with balanced 50 g brass weights, and on the right, the pulley in motion as the...

Large ballbearing rolling on long PASCO track.

Sliding tablecloth out from under posh dinner setting.

What it shows:

A body will remain at rest unless a force acts upon it. So too will your best china remain in place as the table cloth is whipped from under it providing the friction between the cloth and table setting is low, and the speed of removal high.

Two forks, a cork, and a matchstick balance on the lip of a glass.

What it shows:

Balancing two forks in an unlikely configuration is a lesson in finding the center of mass and stable equilibrium. Nothing too deep here, but it's fun.

...

Beam supported at ends with platform scales and toy truck as load to demonstrate moment arms.

What it shows:

The concept of moment arms is exemplified by this model of a truck on a bridge.

How it works...

What are the conditions for stable equilibrium?

What it shows: 

Place different rectangular solids (of various aspect ratios) on a cylinder to demonstrate which ones balance in stable equilibrium.

...

What It Shows

The two ends of a dial-type spring balance are each connected to strings which run over pulleys. With equal weights attached to the ends of the strings, the spring balance indicates the value of one of the weights.

How It Works

The demonstration is presented to the class as a puzzler: the spring balance is turned around so that the class can't see the dial. Students are invited to guess what it is reading. Invariably they guess the sum of the two weights. The lecturer then turns the face of the dial gauge around showing them the error of...

Push-me/pull-me gliders or pendulum glider on air track.

Irregular lamina with marked center-of-mass tossed in air.

What it shows:

The center of gravity fixed in (or outside) the object always orients itself with minimum potential energy on a vertical line below the support point. When an irregular shape is thrown into the air, it is seen to rotate about its marked center of gravity or center of mass (COM).

How it works:

We have several irregular lamina to suspend and/or throw in the air. They are (1) an amoeba shaped piece of masonite pegboard, (2) a cut-out map of the U.S. glued...

Which road is faster? A kinematics concept Puzzler.

What it shows:

Horizontal and vertical motions are independent of each other.

How it works:

Two balls, starting with the same initial...

Ball drops from mast of PASCO cart; its motion can be considered relative to the moving cart or the track frame of reference.

...