A plane can travel with a speed of 80 mi/hr with the respect of the air. Determine the resultant velocity of the plane (magnitude only) if it encounters a 10 mi/hr tailwind

Answer 1

The treadmill he is riding is going his way at 10 mi/hr. He is going another 80 on the treadmill. Therefore his total speed is 80+10 = 90
If it had been a headwind, it would have been 80 - 10 and he would have been late for coffee.