Originally Posted by
pattern_is_full
Run the engine up - will there be a substantial force pushing you backwards, and straining both your arms and the linkage chains? And by way of the chains, pulling backwards on the nacelle?
Y or N?
Yes, of course. But the force on me is precisely because I'm accelerating (redirecting) the airflow, as Smilin_Ed explained in his post.
That's still only one lot of F=MA.
Where do you think the additional contribution to the reverse thrust comes from?