If time travel to the future existed, doesn't that mean that the future has already occurred and that we are living in the past? and the present is in the "future"?

If a substance is in the gas phase, which of qualities of the gas will stay constant? a: volume b: mass c: shape d: position of particles

The air that we breath is made mostly of which gaseous molecule

Water is siphoned from a large tank and discharges into the atmosphere through a 50-mm diameter tube. the end of the tube is b = 2.1 m below the tank bottom which is a = 7.4 m deep, and viscous effects are negligible. determine the maximum height h over which the water can be siphoned without cavitation occurring. atmospheric pressure is 101.4 kpa, and the water vapor pressure is 1.79 kpa (absolute)