Its called the Phase Transition. Im assuming your asking what is it called when matter transitions between solid liquid and gas.
-- Speed = (distance) / (time to cover the distance) = 840/2.5 = 336 m/s
-- Frequency = (speed) / (wavelength) = 336/0.70 = 480 Hz.
Distance = speed x time. The total speed is 30 + 60 = 90km/h and the total time taken is 15 + 15 = 30 minutes. Therefore, you do 90 x 30 = 2700km
Answer = 2700km
