How to Make Spring Scale Science Projects
A spring scale is a weighing scale used to measure pulling force. Experiments for which a spring scale can be used include determining the volume of irregular objects, measuring the leverage provided by pulleys, and exploring engineering load safety. These experiments are all suitable as science projects.
- Difficulty:
- Moderately Easy
Instructions
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Measuring Irregular Volume
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1
Weigh an object hanging from a spring scale in air, and then weigh the same object submerged in water.
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2
Take the difference between the weights.
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3
Convert this difference to grams. For example, 1 kilogram is 1,000 grams and 1 pound is 454 grams. The number of grams equals the number of cubic centimeters of the object, which is the volume. This calculation follows Archimedes' principle and the fact that water weighs 1 gram per cubic centimeter. Archimedes' principle states that the buoyant force on a submerged object equals the weight of the water it displaces.
Mechanical Advantage
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1
Attach the bottom hook of a spring scale to a load. Attach the top hook to the bottom eyelet of a double-pulley block. Double-pulley blocks are available at mountaineering shops. If you can't find them locally, please refer to the links provided below.
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2
Attach the double-pulley block to a stable support above the load, through one of its two eyelets. Use a support that will comfortably sustain the weight of the load you are using.
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3
Thread one end of string or rope through one of the pulleys in the hanging block. Call this end of the rope end A. Thread the rope down into one of the pulleys of the load-attached block. Thread it up through the unused pulley of the hanging block, down again through the unused pulley of the load-attached block. Thread the rope up again to the hanging block, and tie it to the unused eyelet on the bottom of the hanging-pulley block.
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4
Attach a second spring scale to the other end of the rope (end B) by its top hook, and pull it by its bottom hook to lift the load off the ground. The number of doublings of line should lead to a mechanical advantage of 4-to-1, leading the scale reading at end B to be only a quarter of the force reading of the load-attached spring. In other words, the input force is magnified four times. Whatever the weight of the load, only one fourth the force is needed at end B to support its weight off the ground as if the doubling up of the line hadn't been done.
Hyatt Regency Walkway
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1
Hang four spring scales from a solid horizontal rod, with equal weights hanging off the bottom hook of each scale. Write down the scale readings.
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2
Now stack the scales as follows: the top hook of each scale hangs on the bottom hook of a scale above it. The topmost scale hangs off the bar. Each scale still has its original weight hanging off its bottom hook. This will make a chain formation, or stacked effect, with one scale hanging off the bar.
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3
Record each scale's reading. Compare the results to the earlier readings, when the scales were all hanging directly off the horizontal bar. The results are similar to the difference of several men hanging onto a rope, one man above the other, versus one man hanging onto the rope, each man hanging onto his legs, with the top man bearing the weight of everyone.
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1
Tips & Warnings
The last experiment illustrates the difference between the architect's drawings and the implementation of those drawings, which led to the collapse of suspended walkway at the Hyatt Regency in Kansas City. The 1981 collapse killed 114 people.
Check the weight limit of the double-pulleys to make sure you don't hang more weight on them than they can sustain.
