TRIPLE BEAM BALANCE


The triple beam balance is a rugged, inexpensive weighing instrument. It is named for the three beams which carry weights.
A. The middle beam reads only in 100 g increments.
B. The far beam reads only in 10 g increments.
The weights in each of these must always sit in a "notch". They cannot be placed at arbitrary points on the beam.
C. The weight on the front beam can be placed to read continuously from 0 to 10 grams.
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Triple Beam Balance
What does a can of diet Mountain Dew weigh?
The Triple Beam Balance is a typical mechanical balance.
It has a beam which is supported by a fulcrum. On one side is a pan on which the object is placed. On the other side, the beam is split into three parallel beams , each supporting one weight. In measuring the weight of an object, rather than adding additional weights, each of the three weights can be slid along the beam to increase their lever arm.
It works just like a tetter-totter. If you have two people of unequal weight, the heavier person sits closer to the fulcrum to decrease their lever arm.

Making a Weighing

In measuring the mass of any material ,
you must always make
............................................. two weighings!
If you use a container to hold the material, you must first weigh the empty container. This weight is called the
tare of the container. Then you weigh the container with the material in it. The difference between these two weighings is the mass of the material.
In weighing an object directly on the pan, you must still make two weighings. The first of these is to weigh the empty pan! This must be set to read 0.00 g. The triple beam balance has a little knob under the pan which you screw in or out to set the empty balance to read exactly 0.00 g.
So, in weighing an object directly on the pan, you must first
Zero the balance. Only if the balance is properly zeroed, will it weigh the object correctly.

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For a better view, open this image

Reading the mass of the Diet DEW

Rear weight is in the notch reading...... 70 g
Middle weight is in the notch............... 300 g
Front beam weight reads.....................
.........3.34 g

The can of soda weighs......................... 373.34 g

The front beam is graduated in one gram units 0-10 (see numbers). Each one gram interval is further divided into 10 spaces or .1 gram. When the weight is carefully placed, its position can be estimated to .01 or .02 g.

In reading any graduated scale....
You read not only to the smallest graduation mark but
estimate between the graduation marks.
This is called reading the scale to the proper number of
Sig Figs.

RWK 11/97