Concrete block smashed on lecturer's chest with sledge hammer.

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.

How it works:

The forces (weight of the body, cinder block, etc.) are distributed over the total area of all the nail...

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.

Block and tackle, or a simple pulley, attached to hall ceiling for lecturer to hoist self.

Upright board or Blackboard Mechanics with pulley combinations.

Cardboard animal jaws as examples of levers.

What it shows:

The biting force of an animal depends upon the magnitude, direction and point of application of forces exerted by the jaw muscles. A mammalian jaw exerts a greater force than does a reptilian jaw despite a more delicate joint structure, because evolution has improved the physics of eating.

How it works:

The demonstration consists of two dimensional cardboard models of reptilian and mammalian lower jaws (see figure 1). Both are about 30cm in length. They are pivoted...

What it shows:

One falling domino knocks down two, which in turn knock down three, etc. Use it to model cascade signaling.

How it works:

Twenty five rows of dominoes are set up in front of the first domino. Each successive row is comprised of one additional domino, e.g. the 2nd row has two, the 3rd row three, ... the 25th row has twenty five. A total of 325 dominoes get knocked down in a couple of seconds after the 1st one falls.

The action can be contrasted to a second board which has 11 rows of 30 tiles each, for a total of...

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.

...

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...