( ( To ( prevent ( ( the glass ) ( bending ( under gravity ) ) ) ) ) ( , ( ( its weight ) ( ( is ( carried ( by ( ( ( many ( distributed ( reaction forces ) ) ) , ) ( which ( should ( ( change ( with orientation ) ) ( to ( mimic ( ( the ( buoyant force ) ) ( felt ( if ( ( the mirror ) ( were ( floated ( in ( liquid ( of ( its ( own density ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (S (VP (TO To) (VP (VB prevent) (NP (NP (DT the) (NN glass)) (VP (VBG bending) (PP (IN under) (NP (NN gravity)))))))) (, ,) (NP (PRP$ its) (NN weight)) (VP (VBZ is) (VP (VBN carried) (PP (IN by) (NP (NP (JJ many) (VBN distributed) (NN reaction) (NNS forces)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (MD should) (VP (VB change) (PP (IN with) (NP (NN orientation))) (S (VP (TO to) (VP (VB mimic) (SBAR (S (NP (DT the) (JJ buoyant) (NN force)) (VP (VBD felt) (SBAR (IN if) (S (NP (DT the) (NN mirror)) (VP (VBD were) (VP (VBN floated) (PP (IN in) (NP (NP (NN liquid)) (PP (IN of) (NP (PRP$ its) (JJ own) (NN density))))))))))))))))))))))) (. .)))
To prevent the glass bending under gravity, its weight is carried by many distributed reaction forces, which should change with orientation to mimic the buoyant force felt if the mirror were floated in liquid of its own density.
(ROOT (S (SBAR (IN If) (S (NP (DT the) (JJ buoyant) (NN force)) (VP (VBZ is) (ADJP (ADJP (JJR greater)) (PP (IN than) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity)))))) (S (VP (VBG acting) (PP (IN on) (NP (DT a) (NN ship)))))))) (, ,) (NP (PRP it)) (VP (MD will) (VP (VB float))) (. .)))
If the buoyant force is greater than the force of gravity acting on a ship, it will float.