An object of mass 100 kg is tied to the bottom of a pond with a light chain. If the tension in the chain is 200 N, what is the mass of water displaced by the object ?
Hmmmm. Does the chain have weight? Ok, a weightless chain.
tension=mg-bouyancy
200=100*9.8-bouyancy
solve for bouyancy, then masswater=bouyancy/9.8N/kg