Hooke's law determines the size and direction of the force in a compressed spring. For a compressed spring, the force points in the direction opposite of the compression direction. The force directly depends on the linear distance the spring has been compressed and a quantity know as the spring constant. The spring constant is unique to a given spring and is found experimentally by hanging an object from the spring hung vertically. The amount of weight hung on the spring and the distance it stretches allows you to calculate the spring constant.
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Things you need
- Tape Measure
Hang the spring vertically such that its sides don't touch anything.
Place an object on a scale to determine its weight in pounds. Choose an object that will not make the spring stretch more than half its length, so you do not damage the spring. As an example, say the object weighs 0.227 Kilogram.
Convert the weight of the object to newtons, the scientific unit for weight, by multiplying by 4.45, since a pound is equivalent to 4.45 newtons. Performing this operation, 0.50 times 4.45 equals 2.23 newtons.
Hang the object from the bottom of the vertically hung spring and measure the amount it stretches in centimetres. For the example problem, assume it stretches 10 centimetres.
Convert the stretch distance to meters by dividing by 100, since 100 centimetres are in every meter. Now you have a stretch distance of 10 divided by 100 or 0.10 meters.
Divide the weight of the object by the stretch distance to obtain the spring constant for the spring in newtons per meter. Continuing the example, 2.23 newtons divided by 0.10 meters equals 22.3 newtons per meter.
Lay the spring flat on a table with one end against a wall.
Compress the spring towards the wall with one hand while you measure the distance in centimetres the spring has been compressed with your other hand. As an illustration, assume it has been compressed 5 centimetres.
Convert the compression distance to meters. Accomplish this by dividing by 100. Now you have compression distance of 5 divided by 100 or 0.05 meters.
Multiply the spring constant by the compression distance to solve for the compression force in newtons. Completing the sample problem, 22.3 newtons per meter times 0.05 meters yields a compression force of 11.2 newtons.
Tips and warnings
- Metric units must be used when employing Hooke's law.
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