Dear Student, Energy conservation applying – K Ei + P Ei = K Ef + P Ef 0 + mgi – Buoyant forcei = 0 + mgf – Buoyant forcef + W D => [500 x a3 x g] – [1000 x (1/2) x 45x60 x 10-4 x 30 x 10-2 x g] = [500 x a3 x g] – [1000 x 45x60 x 10-4 x 30 x 10-2 x g]+ W D =>[1000 x 45x60 x 10-4 x 30 x 10-2 x g] - [1000 x (1/2) x 45x60 x 10-4 x 30 x 10-2 x g] = W D => W D = [1000 x 45x60 x 10-4 x 30 x 10-2 x 10] = 810 J Regards

pl ans Q21
pl ans Q21 21• A cubical block of wood has density = 500kg/m3 and side I = 30cm. It is floating in rectangular tank partially filled with water of density p2 = 1000kg/m and having base areaA=45cmx60cm. Calculate the work done (in joule) to press the block slowly so that it is just immersed in water. your answer in J)

Dear Student,

Energy conservation applying –

K.E_i + P.E_i = K.E_f + P.E_f

0 + mg_i – Buoyant force_i = 0 + mg_f – Buoyant force_f + W.D

=> [500 x a³ x g] – [1000 x (1/2) x 45x60 x 10^-4 x 30 x 10^-2 x g] = [500 x a³ x g] – [1000 x 45x60 x 10^-4 x 30 x 10^-2 x g]+ W.D

=>[1000 x 45x60 x 10^-4 x 30 x 10^-2 x g] - [1000 x (1/2) x 45x60 x 10^-4 x 30 x 10^-2 x g] = W.D
=> W.D = [1000 x 45x60 x 10^-4 x 30 x 10^-2 x 10] = 810 J

Regards

-7

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