Centrifugal Force and Other Strange Matters
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### Lecture Description

The name "centrifugal" force given to certain events is very often badly used. Consider a car going round a curve. A book lies on the seat beside you. You are the driver. You take a curve to the left - say. As you make the curve you see the book move radially out on the seat - moving toward the door. NO! This is not right! You make the curve. The car makes the curve. The book keeps on going in a straight line - tangent to the curve. It does not move radially outward. We show some DEMONSTRATIONS on these matters.

A - We whirl a ball on a string in a vertical circle. At the top of the
circular path we let go of the string. What does the ball do? Does it go radially outward? NO. It goes off in the direction it was going -tangent to the path. This is Newton's First Law again. See Program *2.

B - A device has two spheres in it - lying in a circular trough. To get each
sphere to ITS end of the trough we spin the device about a central vertical axis. The balls get to their respective slots at the ends but they do not fly radially outward.

C - IN THE PARADOX OF THE ROTATING CANDLES we spin the apparatus about a central vertical axis - as in B above - but this time a paradox arises. The candle flames lean INWARD. HINT: The density - the "heaviness" of the flames - is less than that of the air in the protecting chimneys.

D - In the classic of whirling a bucket of water in a vertical circle it is always said: " If you don't go fast enough the water will fall out" . NO. This is not right. For when the motion is too slow to make the circle the bucket will fall along with the water! OK?

E - On the forces which arise in rotation we show: (a) Why the Earth is flattened at the Poles; (b) How a "governor" works; (c) A coin on a coat-hanger; (d) A String in a Glass Tube; (e) A limp rubber loop rolls off as a rigid body; (f) A lasso; (g) Emptying a jug of water in the quickest way.

We raise an added dilemma with a toy gun which "rolls" a hoop away and then — e -coo "rolls" back! Question: How can a hoop ROLL AWAY - rolling in one direction - and roll back - still rolling? ANSWER: It can not! So - if we look circumspectly at the Physics of this we discover an enchanting thing.

The hoop was NOT rolling away - Got it?
NOTE: This business of Centrifugal Force is very troublesome for beginners -indeed for everybody. What we see happen in circular motion really depends upon where the observer is. Which brings us to the subject of Relativity.

### Course Description

Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.

This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.