Question

How can buoyant forces be measured?

Answer 1

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.