Thousands of years ago, giraffes with short necks were common within giraffe populations. nearly all giraffe populations today have long necks. this difference could be due to

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.

Which of the following is not a part of the respiratory system? a. pharynx b. trachea c. pancreas d. larynx

Acar drives toward the right over the top of a hill, as shown below. which arrow represents the centripetal acceleration? w x y z