NEET-XII-Physics
pp year:2018
- #8A small sphere of radius 'r' falls from rest in a
viscous liquid. As a result, heat is produced due to
viscous force. The rate of production of heat when
the sphere attains its terminal velocity, is
proportional to :-
(1) ``r^3``
(2) ``r^2``
(3) ``r^5``
(4) ``r^4``digAnsr: 3Ans : (3)
Sol. Rate of heat produced
= v T
dQ
F V
dt
=
2
T
2r
V ( )g
9
= 6rVT × VT ∴ VT r
2
2T
dQ
rV
dt
VT r
2
5
dQ
r
dt