Q. An ambulance moving at 42.0 m/s sounds its siren whose frequency is 450 Hz. A car is moving in the same direction as the ambulance at 25m/s. What frequency does a person in the car hear (a) as ambulance approaches the car? (b) After the ambulance passes the car?
Q. Fred and Barney are two electric charges that are to begin with held 1 meter apart and experience an electric repulsion of 10 pounds of force. What would be the force of repulsion between them be if the two were moved closer together so that they were now ¼ meter apart?