Question

A thermoflask containing tea is shaken vigorously.
Considering tea as a system
(a) has heat been added to tea?
(b) has work been done on it?
(c) has its internal energy changed?
(d) does its temperature rise?​

Answer 1

A thermoflask containing tea is shaken vigorously.

Considering tea as a system

(a) has heat been added to tea?

(b) has work been done on it?

(c) has its internal energy changed?

(d) does its temperature rise?​

Answer :

a. No , heat is not transfered from the surrounding.

i.e. d Q = 0

b. Yes , work is done in shaking against the viscous force .

i.e. d W = - ve .

c. Yes , internal energy of tea increases , as

d U = d Q  -  d W

d U =  + ve   [ d Q = 0  and d W = - ve ]

d . Yes the temperature of tea rises due to increase in  internal energy.