Nature of process of application of breaks in a vehicle - Thermodynamics
Q. A process of application of breaks in a vehicle is- Published on 20 Aug 15a. a reversible process
b. an irreversible process
c. a quasi-static process
d. none of the above
ANSWER: an irreversible process
In the process of application of breaks in a vehicle the kinetic energy of the wheel is transferred to the break flywheel and converted into heat energy. As all of the heat generated is not dissipated in the atmosphere and the internal energy of the flywheel increases. Internal energy exists in the form of kinetic energy (K.E.), potential energy (P.E.) and molecular internal energy (U).
Applying balance equation for internal energy,
(K.E.)1 + (P.E.)1 + U1 = (K.E.)2 + (P.E.)2 + U2
As wheel is taken to rest, (K.E.)2 will be zero and there will be no change in P.E.
Therefore,
U2 = U1 + (K.E.)1
There will be an increase in the molecular internal energy by the absorption kinetic energy of the wheel. The reverse of this process that is the conversion of the increase in the molecular internal energy into the kinetic energy is not possible, therefore the process is irreversible.
