Two cars approach each other from opposite directions each with a velocity of 54 km/h. One of the cars emits a note of frequency 480 Hz. What will be the approximate frequency
heard in the other car before they cross each other?

What is the difference between electrically neutral objects and electrically charged objects

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 igneous intrusions and extrusions