Buoyancy Lab Explanation

The following equations express how buoyancy works. The goal of the lab is to find the density of the cylinder based on the buoyant force response.

The equations above are found on your equation sheet. The other equations summarize the net forces in the scenario.

The force diagrams to the right express the forces experienced by the object in and out of the water.

Notice how the out the water Force on the spring is equal to weight and how that can be expressed via density, volume and gravity.

The equation at the bottom for "in the water" is the main equation that we will use.

Rearrange the main equation to show how the Force on the spring is the weight minus the force buoyant. Substitute in the density and volume of the objects for the masses. Our final equation shows what we need to find the density. It looks like we will need the volume of the objects.

Begin with the main formula again, but this time solve in a way that shows the differences between the forces on the spring in and out of the water must be due to a force buoyant. Your ultimate goal is to solve for Volume.

Now we can substitute in the equation for volume into the equation for density.

Here is the final equation. Can you read what it says? You should be able to decode it.

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