I feel kinda stupid asking this, since I have a bachelor's degree in physics. But, here it goes: I'm doing a thought experiment on my own (i.e., not a homework problem) for a hypothetical vacuum airship. I've determined the following quantities: V_displaced = 15 m^3 m = 13.5 kg F_net = F_buoyancy - Weight = 44.0 N upwards a = 3.26 m/s^2 upwards I'm assuming that winds are calm (i.e. v_wind = 0), and I've not factored in how pressure and density change over altitude. Again, I feel like a dunderhead for asking this, but using these quantities, how can I calculate range and altitude? All the equations I know involve the use of initial velocity, but the only forces acting on the airship are gravity and the buoyant force.