Question

Two trains on separate tracks move toward each other. Train 1 has a speed of 130 km/h; train 2, a speed of 90.0 km/h. Train 2 blows its horn, emitting a frequency of 500 Hz. What is the frequency heard by the engineer on train 1 when the air temperature is 16^oC?

Answer 1

$$f=f_0\frac{c+v_r}{c-v_s}$$

$$f=500\:\rm Hz*\frac{1226.87\: km/hr+130\: km/hr}{1226.87\: km/hr-90.0\: km/hr}$$

$$f=597\:\rm Hz$$