Answer
a) When the acceleration is zero, the rod falls with constant speed.
b) clockwise
c) $v=\frac{mgR}{B^2L^2}$
Work Step by Step
(a) We know that initially the rod falls due to acceleration from gravity. When the induced current begins to flow, the upward magnetic force opposes its downward fall and acceleration is decreased. Thus, when the acceleration is zero, the rod falls with constant speed.
(b) We know that as the rod falls, the magnetic flux increases and it causes an increase in the induced emf and as a result the current flows in the clockwise direction.
(c) We know that the downward force due to gravity is opposed by the magnetic force
so $ mg=IBL $
$\implies I=\frac{mg}{BL}$
We also know that $ v=\frac{IR}{BL}$
$\implies v=(\frac{R}{BL})(\frac{mg}{BL})$
$\implies v=\frac{mgR}{B^2L^2}$
