Kennedy spent much of the first quarter on the bench after a heavy collision with Lachie Henderson left him struggling to get up, but he showed no ill-effects with his long bomb late in the second.
With the forward 50 open, Kennedy kicked from long range and it took a friendly bounce to roll into the goals after Carlton's Dennis Armfield ran past it.
The key forward's goal capped a second quarter where the Eagles outscored the Blues eight goals to three to recover from a 16-point quarter-time deficit.
