Final answer:
The weighted brackets on a triple beam balance are called poises. They are adjusted to measure the mass of an object when the balance is leveled.
Step-by-step explanation:
The three weighted brackets that slide across the beams of a triple beam balance are called poises. Each poise is set to a precise mass measurement on the beams, typically marked in grams. The smallest poise may measure increments as fine as 0.1 grams, while the larger poises measure in larger increments, for example 10 grams and 100 grams respectively. When all three poises are set correctly, so that the balance is leveled at zero when empty, one can place an object on the balance pan and slide the poises to find the correct mass. The combined value of where all the poises rest gives the total mass of the object. Triple beam balances are commonly used in educational settings for hands-on learning about mass and weight.