# Laboratory

## Experiment: Buoyancy

In Drilling Fluid: Lifeblood of the Well, you can find out about the many functions of drilling fluid—the liquid that fills the borehole of a well as it is being drilled. One of these is buoyancy, the ability of a liquid to partially support the weigh of an object, in this case, the steel drill pipe. Here's a demonstration of how this works.

### Tools and Materials

• Tall glass or graduated cylinder
• Large screw or bolt
• Water and at least one other liquid, such as corn syrup
• Spring scale

### What to Do

1. Tie one end of the thread around the screw. Make a loop at the other end to hang on the hook of the spring scale.
2. Weigh the screw and record your result.
3. Submerge the screw in water and weigh it again, making sure it is fully submerged but not resting on the bottom of the container or against the sides.

 Object: Volume of object (cm³): Density of object (g/cm³): Fluid Density of fluid (g/cm³) Weight of object (g) air water corn syrup

Now repeat the procedure with a different liquid. We used corn syrup; you might also try glycerine or corn oil. Use a table like this to record your results.

• How does the weight of the screw in air compare with its weight in water?
• How do these two weights compare with the weight in corn syrup and any other liquids you used?
• Can you calculate the volume of the screw?
• Can you calculate the density of the corn syrup and the other liquids?

Take a look at our results.

 Note: Grams are a measure of mass, not weight. If an object has a mass of 10 g (4 oz) on Earth it will still have a mass of 10 g on the Moon. But on the Moon it would weigh less because the force of gravity is weaker. Since we are staying on Earth for this experiment, gravity doesn't change and we can reliably use weight as an indicator of mass. It is common to use the gram as a unit of weight.