By using standard masses , like grams and kilograms , an unknown object 's mass can be determined when it balances with an equal amount of known standard masses .
(an unknown object 's mass; can be determined; T:when it balances with an equal amount of known standard masses) (it; balances; with an equal amount of known standard masses)
an unknown object 's mass it
can be determined balances
T:when it balances with an equal amount of known standard masses
with an equal amount of known standard masses