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This equation is for a body (a ball, an arrow, a toy rocket) which is thrown vertically up with the initial speed of 307 m/s.
The body participates in TWO movements simultaneously:
1. It moves uniformly verticaly up, and
2. Is falls free with the gravity acceleration of 9.81 m/s^2.
This equation IS NOT for the real rocket launched by NASA, when the working engine provides the acceleration vertically up.
This equation is for the "toy rocket" without the engine, launched with the vertical initial velocity.
I am glad that your post was broken.
It gave me the possibility to educate you a bit.