Atrain traveling 80.0 kph is blowing its horn as it approaches a railroad crossing. the horn has a frequency of 300.0 hz. assume the speed of sound is 331.5 m/s. what is the observed frequency of the horn?

395 hz

281 hz

322 hz

Sawyer is studying diffraction. he draws a diagram of a plane wave to show how light waves travel. which best describes sawyer’s error? the wave fronts should be perpendicular to the direction in which the waves move. the arrow showing the direction of movement of the waves should be pointing to the left. the arrow showing the direction of movement of the waves should be pointing downward. the wave fronts should be both parallel and perpendicular to the direction in which the waves move.

If a rock is thrown upward on the planet mars with a velocity of 12 m/s, its height (in meters) after t seconds is given by h = 12t − 1.86t2. (a) find the velocity of the rock after two seconds. m/s (b) find the velocity of the rock when t = a. 12−3.72a m/s (c) when will the rock hit the surface? (round your answer to one decimal place.) t = s (d) with what velocity will the rock hit the surface? m/s

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?