Atrain is moving parallel to a highway with a constant speed of 19.5 m/s. a car is traveling in the same direction as the train with a speed of 40.5 m/s. the car horn sounds at a frequency of 512 hz, and the train whistle sounds at a frequency of 322 hz. (a) when the car is behind the train, what frequency does an occupant of the car observe for the train whistle? hz (b) after the car passes and is in front of the train, what frequency does a train passenger observe for the car horn?

Scientists use laser range-finding to measure the distance to the moon with great accuracy. a brief laser pulse is fired at the moon, then the time interval is measured until the "echo" is seen by a telescope. a laser beam spreads out as it travels because it diffracts through a circular exit as it leaves the laser. in order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. staying within this diameter is accomplished by using a special large-diameter laser. part a if λ = 540nm , what is the minimum diameter of the circular opening from which the laser beam emerges? the earth-moon distance is 384,000 km. express your answer to two significant figures and include the appropriate units.

What are segments of dna that code for a particular trait. a combination of dna and proteins make up what

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force