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Pulley Board

Upright board or Blackboard Mechanics with pulley combinations.

pulley board

Elastic and Inelastic Collision Model

What it shows:

Two cars have the same mass and same spring bumper. When given a push and allowed to collide with a wall, one car bounces off with only a small reduction in speed ("elastic" collison) whereas the other car comes nearly to a complere stop ("inelastic" collision).

How it works:

There are two impulse cars made of identical materials and have the same mass. The car that models an elastic collision has all its lead sinkers securely attached to the frame so that they can't move. In contrast, the car that models an inelastic collision has the lead sinkers...

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Center of Percussion

The motion (or lack of motion) of the suspension point of an object is observed when the object is struck a blow.

What it shows

The center of percussion (COP) is the place on a bat or racket where it may be struck without causing reaction at the point of support. When a ball is hit at this spot, the contact feels good and the ball seems to spring away with its greatest speed and therefore this is often referred to as the sweet spot. At points other than this spot, the bat or racket may vibrate or even sting your hands. This experiment shows the effect by demonstrating what...

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Molecular Size

Also known as the Ben Franklin pond experiment, after a story in B.F's autobiography.

Olive oil with a known volume is dropped onto water. The water has been dusted with lycopodium powder, which floats on the surface. The oil drop expands, pushing the powder aside to form a clear circle, until the oil forms a monolayer. Measuring the area of the monolayer, dividing the volume of the drop by that area, gives the thickness of the monolayer, which is the height of the oil molecule on water.

From our demonstration movie, we found these values. The size of the patch was 62 cm...

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Motional emf

What it shows

An emf is induced between the ends of a wire moving back and forth in the presence of a magnetic field.

How it works

The ends of a monochord wire are connected to an oscilloscope as illustrated:

Motional emf

Plucking the wire...

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Hero's Shortest Path

What it shows:

Hero's Principle states that light undergoing a reflection from a plane surface will follow the path of least distance. Here is a mechanical analog showing that when the angle of incidence equals the angle of reflection, the path length is minimized.

How it works:

The light path is represented by a 2m length of nylon rope that runs from a fixed end, 'reflects' around a pulley, back up to a second pulley (figure 1). The surplus rope is held taught by a 1kg mass. The pulleys, 6cm in diameter are free to move...

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Syrup Tube

What it shows:

Linearly polarized light, propagating down a long glass tube filled with corn syrup, is made to rotate its direction of polarization by the optically active corn syrup. The intensity of the 90° scattered light varies dramatically, in a periodic manner, along the length of the tube -- the intensity being zero when the dipole radiators oscillate in the line of sight direction, and maximum intensity when they oscillate perpendicular to the line of sight. Scattered light is most intense when the electric field vector is perpendicular to the line of sight.

...

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α, β, γ, n Sources and Detection

What it shows:

Radiations originating from atomic and nuclear processes are classified into four types:

charged particulate radiation consisting of
1. heavy charged particles (α)
2. fast electrons (β)
uncharged radiation consisting of
3. electromagnetic radiation (γ, x-ray)
4. neutrons (n)

The interaction processes of each type of radiation explain their penetrability through matter, their difficulty or ease of detection, and their danger to biological organisms. The interactions of these radiations with matter are unique and the...

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