Final answer:
The water tank on a flight may typically be filled to 100% before departure, but the actual water level during a flight depends on usage and cannot be determined without more information. The volume of air in a passenger's stomach at cruising altitude will increase due to the drop in cabin pressure, according to Boyle's Law.
Step-by-step explanation:
The question how full a water tank would be on a flight more than 4 hours is not a standard physics question, and there is no context provided to calculate or estimate water usage on a flight. Normally, airplanes are equipped with water tanks that are filled to capacity to ensure there is enough water for passengers and crew during the flight. The tank could be filled to 100% before departure, but the actual level during the flight would depend on usage and cannot be precisely determined without additional information such as the size of the tank, the number of passengers, flight duration or water consumption rates.
For the question regarding the volume of air in a passenger's stomach at cruising altitude, we use the ideal gas law which states that the pressure and volume of a gas are inversely proportional at a constant temperature. If the pressure in the cabin decreases, the volume of the gas would increase assuming the temperature remains constant. This is known as Boyle's Law, specifically P1V1 = P2V2 where P is pressure and V is volume. If the cabin pressure drops to 7.50 × 104 N/m², and the initial pressure at sea level is approximately 101325 N/m², you can set up the equation with the initial pressure and volume and solve for the new volume (V2).