As shown in figure a paddle wheel coupled to a mass of 12 kg through fixed frictionless pulleys. The paddle is immersed in a liquid of heat capacity `4200(J)/(K)` kept in an adiabatic container. Consider a time interval in which the 12 kg block falls slowly through 70 cm.
(a) How much heat is given to the liquid?
(b) How much work is done on the liquid?
(c ) Calculate the rise in the temperature of the liquid neglecting the heat capacity of the container and the paddle.

Explanation

(a) No heat is transferred, hence, temperature increases due to work done by paddle in rotation. (b) Loss in potential energy of block
`mgh=12xx10xx0.7=84J`
(c ) `m's Delta theta=84`
`4200DeltaQ=84`
`Delta theta=0.02^@C`