F = m ˙ ( V w 2 − V w 1 ) = m ˙ ( V f 2 tan ⁡ α 2 − V f 1 tan ⁡ α 1 ) {\displaystyle F={\dot {m}}\left(V_{w2}-V_{w1}\right)={\dot {m}}\left(V_{f2}\tan \alpha _{2}-V_{f1}\tan \alpha _{1}\right)\,} (from velocity triangle)