Question

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Answer 1

The bottle rocket has to constantly fight against the constant force of gravity. Gravity is trying to pull it back down to earth.

Not quite sure what you mean by "variables for the bottle rocket" but here's 4 variables which affect the flight of the rocket:
- Wind
- The angle at which the rocket is launched from
- Aerodynamics of the rocket
- The amount of force from the water pushing it up

Answer 2

thanx :)