Astationary police car emits a sound of frequency 1200 hz that bounces off a car on the highway and returns with a frequency of 1250 hz. the police car is right next to the highway, so the moving car is traveling directly toward or away from it. (a) how fast was the moving car going? was it moving toward or away from the police car? (b) what frequency would the police car have received if it had been traveling toward the other car at 20.0 m/s?

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?