If an airplane is headed due north at 120 km/hr directly into a headwind (due south) of 15km/hr, what is the resultant velocity of the aircraft? Only give the magnitude as your answer.

The two most prominent wavelengths in the light emitted by a hydrogen discharge lamp are 656(red) and 486 (blue). light from a hydrogen lamp illuminates a diffraction grating with 500 lines per mm, and the light is observed on a screen 1.50 behind the grating. what is the distance between the first-order red and blue fringes?