How to Build a Spring Scale

Scales made from springs measure weight by how far the springs stretch.

According to scientist Robert Hooke, the opposing force of a spring is directly proportional to the amount by which the spring is stretched. This means that the more weight you apply to a spring, the further it stretches. The spring will also snap back with more force. You can test this theory yourself by creating a spring scale. Just be careful not to stretch your springs too far; if you pull too hard, the springs will not bounce fluidly any longer.

Things You'll Need

• 3-foot wooden board
• Two metal springs: same type
• Industrial stapler
• Two chairs
• Measuring tape
• Two small metal buckets
• Weight objects: marbles, water, magnets, stones, sticks, etc.

Instructions

1. Lay your wooden board on a flat, clean surface. Place the springs in the center of the board, spacing them about 1 foot apart.

2. Press the top coil of each spring against the board while pushing the rest of the coils to the side. Staple the top coil of each spring to the wooden board with an industrial stapler. Tug on the springs to ensure they're secure.

3. Set two chairs about 2 feet apart. Lay the board like a bridge between the backs of the two chairs. This is your spring scale, ready for use.

4. Measure each spring from top to bottom with a measuring tape. Mark down both lengths; they should be exactly the same or within 1/8 inch of each other.

5. Slip a small metal bucket on the last coil of each spring. Measure the springs again to account for the weight of the buckets.

6. Fill the buckets with different materials, measuring the springs each time. The longer the spring, the heavier the object.

References

• Science Buddies: Make Your Own Spring Scale
• Eastern Illinois University: Excursions in Physics