The 7th graders are bouncing along in science this winter exploring the properties of springs. The first part of this exploration is to find out what a spring constant is. When you think about a spring, there are many words that come to students' minds to phrase how springs differ: Stretchiness, bounciness, easier to squish, harder to pull apart. Students work in partners to actually measure this property of many springs called a spring constant. We began by examining our tools- centimeter rulers and newton scales. After an introduction to the metric system and thinking about the usefulness of units when trying describe a phenomenon to be measured, we got to work on our first project: calculating the spring constants of newton scales.

For the uninitiated, a newton scale is a spring inside of a tube that has markings on it that measure both mass in kg (as a function of gravity) and Force measured in N (newtons).

Students weighed some random objects from around the room to have them extend the spring of the scale, and measure the change in length of the spring known as displacement in cm. They would record the Newtons, and the centimeters, in order to calculate the spring constant. Here are some examples.

Lastly, we had to do some calculations to make our data sing, and tell us the spring constant of the springs inside the newton scales. In true scientist fashion, we had to use some algebra to start us off. F=-kx. This formula shows the relationship between the force applied by a spring (F) (negative because it's in the opposite direction as the force applied to it!) over a given distance of compression or extension X multiplied by the spring constant K. And if you use the handy dandy algebra rule of you can change an equation any way you like, as long as you do the same thing to both sides, you can divide both sides by X and rewrite the equation to read (F/X)= -k. Using this equation we can plug numbers into a spreadsheet to find the spring constant of any spring once we know the N of force and the cm displacement.

We gathered our whole class's data to find an average for each spring's constant. Students discussed the reasons we would want many data points and came up with ideas like "it will help to show any results that don't match" and "the results might be different depending on our own mistakes"

Next up we calculate the spring constants of mystery springs that we will then use to build marble launchers and do more math about the efficiency of the launcher's ability to convert potential energy to kinetic energy!

Spring Science Investigations in 7th Grade

Thinking About Skin With the Forest Primes (K/1)

Making a Family Book in the Puzzle Primes (3 year-olds)