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1994

# Reflections

George Vanderkuur, Malvern Collegiate, Toronto

A laser, chalk dust and right-angle corner made of mirror tiles show the retro-reflection of light from a corner cube mirror. (Safety note: use a low-power laser beam and take care to avoid directing the beam into the audience.) Students will also enjoy looking into the mirror and observing that the image of their face (or open eye) is always in the corner. Try this with one eye closed. Read More...

# Flipping for Physics

John Wylie, The Toronto French School

Here is a good demonstration that can be used in its simplest form to show stable and unstable equilibria or, in a more advanced version, to illustrate some finer points about moments of inertia and angular motion. The material needed could not be simpler. You need a board. There are no special requirements here except that the board be rectangular and have three distinctly different dimensions. In a pinch, I have used a good-sized physics text book held closed by a strong elastic. Most brief cases work and if students feel lucky, they can try out their calculators. Read More...

# Huge Pendulum, Centre of Mass, and Magnetic Force

John Earnshaw, Trent University

The author presents three demonstrations: a large pendulum, the centre of mass of a person, and the magnetic force on a beam of electrons. Read More...

# Colour Mixing the Economical Way

Bill Konrad, Chatham Kent Secondary School

I am sure that, in the schools of Ontario, the range of equipment presently in place to demonstrate colour mixing varies all the way from ray boxes with colour filters to expensive projectors specifically designed for that topic. Many of these may be effective but frequently one finds that the resulting colour is not exactly what theory predicts. For example, a blue light, a green light, and a red light projected onto the same area of a white screen may produce a “yellow” white or a “greyish” white. The demonstration described below gives excellent results and, in keeping with current budget constraints, is very economical. To carry it out, proceed as follows. Read More...
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