Assume that the porsche's maximum speed is 78.0 m/s and the police car's is 58.0 m/s. at the moment both cars reach their maximum speed, what frequency will the porsche driver hear if the frequency of the police car's siren is 440 hz? take the speed of sound in air to be 340 m/s.

The police's car is chasing the porsche with a speed 58.0 m/s. The porsche is moving with speed 78.0 m/s: this means that the porsche is moving away from the police's car by (78.0 - 58.0) m/s = 20.0 m/s.

Because the porsche is moving away from the source of the siren (the police's car), the frequency the porsche's driver hear will be shifted according to (Doppler effect):

where c=340 m/s is the speed of sound, f=440 Hz is the original frequency of the sound, and vs=20 m/s is the relative speed of the porsche with respect to the police's car. Substituting, we find the frequency f' at which the porsche's driver will hear the siren:

Answer: it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.explanation:   we have equation of motion ,where s is the displacement, a is the acceleration, u is the initial velocity and t is the time taken.average velocity = displacement/ time taken.average velocity = 10.69 miles/hr = 10.69*1.6*1000/(60*60) = 4.75 m/s4.75 = s/ts = 4. 1we also have acceleration = 2.18 m/s², initial velocity = 0 m/sso it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.

Answer;

hot magma rises and pushes up toward the lithosphere, and as it cools it cycles back down toward the core to be heated again.

explanation; convection currents are the circular pathways taken by a fluid that enhances heat transfer by the process known as convection which occurs in fluids.convection currents transfer heat from one place to another by mass motion of a fluid. earth mantle is in a semi-liquid state and behaves like any other fluid, rising up from the bottom of the mantle after becoming hotter and less dense from heat of the earth's core, as the rock loses heat into the earth's crust it becomes cooler and more dense, then sinking back down to the core, then repeating the cycle.