If there's no air resistance, then there's nothing that has any effect on his forward velocity. It's still 40 m/s forward, and it WILL be until he hits the ground.
The skydiver's forward velocity remains at 40 m/s after 1 second because there is no air resistance or other forces acting in the horizontal direction. Thus, the initial forward velocity is maintained throughout the fall. In conclusion, after 1 second, the forward velocity is still 40 m/s.
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