What does the doppler modal velocity represent

At what time will the interfering waves have an amplitudeof zero?

The diagram shows a wave. the quantity shown is the amplitude. this quantity is directly proportional to which of these other quantities? a) energy b) frequency c) period d) wavelength

A980-kg sports car collides into the rear end of a 2300-kg suv stopped at a red light. the bumpers lock, the brakes are locked, and the two cars skid forward 2.6m before stopping. the police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact. what was that speed?