Abalance is used for measuring mass of an object, and beam balances, like a seesaw, measure an unknown mass by comparison to known masses. Given these facts, an object that can be used for measuring mass of an object is similar to what playground item among the following options:
- forces
 - Slide
 - barrel
 - Seesaw
 - Merry-go-round
 - rockets
 - Monkey bars
 - matter


 

    Seesaw     