Show why objects float in a prefered orientation and why one hull shape is more stable than another.

... Read more about Stability in Flotation

Vector representation of position, velocity, and acceleration.

What it shows:

A circular train track¹ is mounted on a board. X-Y axes are painted on the board with the origin at the center of the circle. Vector Arrows (Newtonian Mechanics, Vectors and Forces in Equilibrium) representing position, velocity, or acceleration may be attached to the train to...

The concept of pressure is demonstrated by lying on a bed of nails.

What it shows:

The lecturer (or someone else) lies on a bed-of-nails without discomfort, thus demonstrating the concept of pressure, which is the force per unit area. For added drama the person is sandwiched between two beds of nails with the added weight of a cinder block on top. The cinder block can be broken with a sledge hammer.

figure 1: A supermarket tabloid reports on how macho man pulls off this stunt.
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Selection of blocks that slide down a variable-angle inclined plane to demonstrate the various aspects of friction.

What it shows:

There are actually three (or more) demonstrations under the wing of this title: (1) A block or box is placed on an adjustable inclined plane which can be raised until the block slides. The tangent of the angle then gives the coefficient of friction between the surfaces. (2) The difference between dynamic and static friction may be demonstrated. A large dial spring balance is used to determine the forces required to drag a box on...

Triangular table supported by platform scales.

What it shows:

This is a two-dimensional version of the Loaded Beam demonstration.

How it works:

An equilateral triangular-shaped table is supported at each corner by a platform scale (same type as in "Loaded Beam"). One of our large (14.5 kg = 32 lb) weights is placed on the table. The scale readings vary with the position of the weight. The procedure to be followed in this demonstration...

Wooden arrow vectors, hand held or mountable.

What It Shows:

Various length and color, wooden arrow vectors can be hand-held, placed (magnetically) on the blackboard, or stuck into a wooden block to define a coordinate system. Small vector blocks can be used as body axes or to visualize coordinate transformations.

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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.

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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...

A dozen blocks are stacked on top of each other over the edge of the table seemingly defying gravity.

What it shows:

N objects of unit length can be stacked on top of each other so that the top object sticks out over the edge of the lecture bench by a distance equal to ¹

1/2 + 1/4 + 1/6 + 1/8 + ... + 1/(2N)

For N approaching ∞, the diverging infinite sum suggests that the top of the pile can stick out an infinite distance. In actuality the divergence is slow, ² and our more practical stack of a dozen 2 × 4 "blocks" can...

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.

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Magnetic blackboard mechanics with spring balances and weights.

What it shows:

Solve a problem in composition of concurrent forces by graphical or trigonometric means.

How it works:

The blackboard mechanics set¹ includes apparatus to demonstrate most of the common laws of statics and some dynamics. The pieces of apparatus are held on the blackboard by magnets and, although not large, are fairly visible in the lecture hall. A booklet with a few dozen suggested demonstration experiments is included in the set.
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Small ladder against wall with variable load and inclination.

What it shows: 

A small ladder is leaned against a vertical wall. A weight can be moved up succeeding steps to find when the ladder will slip and fall down. The forces holding the ladder in equilibrium are in consideration here.

How it works: 

A short (4 foot) step-ladder leans against the wall. The reaction of the wall may be considered horizontal, tangential friction being negligible (the edge of the ladder is covered with a sheet of...

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...

A realistic model of the forces in the erector spinae muscles that support the back when bent over.

What it Shows:

This is an analysis of the tensions in muscles and forces on joints as an application of torques in static equilibrium situations. The muscles involved in supporting the human torso in a stooped position are realistically modeled, and the extraordinary large forces calculated and demonstrated.

How it Works:

When bending over into a stooped position, the principal muscles which support the back are the erector...

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...