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 are chlorofluorocarbons and what impact do they have on the atmosphere?

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

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?