Question

A thermally insulated, closed copper vessel contains water at `15^@C`. When the vessel is shaken vigorously for 15 minuts, the temperature rises to `17^@C`. The mass of the vessel is 100 g and that of the water is 200 g. The specific heat capacities of copper and water are `420(J)/(kg-K)` and `4200(J)/(kg-K)` resprectively. Neglect any thermal expansion.
(a) How much heat is transferred to the liquid vessel system?
(b) How much work has been doen on this system?
(c ) How much is the increase in internal energy of the system?

Answer 1

(a) No heat is transferred, here temperature increases due to work. (The temperature can be increased by supplying heat or by doing work. Heat and work are equivalent.)
(b) `DeltaW=(m_(C)s_(C)+m_(omega)s_(omega))(Deltatheta)`
`=(0.1xx420+0.2xx4200)(17-15)`
`=1764J`
(c ) `DeltaU=DeltaW=1764J`