Sources a and b emit long-range radio waves of wavelength 360 m, with the phase of the emission from a ahead of that from source b by 90°. the distance ra from a to a detector is greater than the corresponding distance rb from b by 150 m. what is the magnitude of the phase difference at the detector?

 The phase difference is 60° with source B ahead

Explanation: Considering the waves A and B emited with an initial phase difference of 90°  and also we must take into account the distance to the detector, in this case the distace rB is shorter 150 m than rA.

Considering the wavelength of 360 m a phase difference of 90° is equal to 90 m in distance,  so source A is ahead this path but the distance to the detector is larger so the difference that both can reach the detector is: 150m -90m = 60 m it is equivalent to 60° in phase each other wave of arriving to the detector. The wave B is ahead.

where are the vectors ?

massxgravity x heght=weightxheight= pe

4900=490xh

h=10