Moments experiment

For this experiment you need a pen or pencil, a ruler and some sweets. I used jelly babies. Starbursts would be good but other brands are available... Balance the ruler on the pencil.

Then put a sweet 10 cm to the left of the pencil.

 This has made the ruler rotate anti-clockwise. The pencil is acting as a pivot. The weight of the sweet acting at a distance away from the pivot creates this turning effect. This turning effect is called a MOMENT. Moment = force x distance from pivot. In this case the force is the weight of the sweet. We are going to say that the weight of the sweet = 1, because we have 1 sweet.

 Now add a sweet on the right hand side. This creates a clockwise moment. Find the distance from the pivot where the ruler balances as best you can. It is very hard to get perfect balance but you can get a feel for the right point.

Next leave the single sweet on the left but balance it with two sweets on the right.

Put your results in a table like this:

In theory, for balance, weight x distance on left = weight x distance on right.
Your experiment will not have been perfect but should be close. I'll be asking you how close.
Finally, what we have just found is called The Principle of Moments
It says "For equilibrium, total anti-clockwise moments = total clockwise moments".