How can buoyant forces be measured?

Here's one easy way:

- - Hang an object from a scale. Write down its weight in air.

- - Keep the object hanging from the scale, but let it down into water,

or whatever fluid you're interested in.

- - Read the scale again. Write down its weight in the fluid.

- - Dry everything off, clean up the lab, and go to your office with your notebook.

- - In your notebook, turn to the page with that day's observations.

Notice that the object's weight in air was greater than its weight in the fluid.

- - Subtract the weight in fluid from the weight in air.

The difference is the buoyant force on the object when it's in the fluid.