A fire engine approaches a wall at 5 m/s while the siren emits a tone of 500-Hz frequency. At the time, the speed of sound in air is 340 m/s. How many beats per second do the people on the fire engine hear?
A. 0
B. 15
C. 29
D. 63
E. 250
Answer: B
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Indicate whether the statement is true or false
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A 1500-kg car traveling at 90 km/h toward the east suddenly collides with a 3000-kg car traveling at 60 km/h toward the south. The two cars stick together after the collision. What is the direction of motion of the cars after collision?
A) 53.1° S of E B) 53.1° E of S C) 36.9° E of S D) 36.9° S of E