I know that when the applied frequency on a mass is equal to the natural frequency, the mass resonates. It has a great amplitude as a result of this. But I don't know how somethings affect the resonant frequency. Like for a mass-spring system. 1) What effect would increasing the mass have on the resonant frequency? 2) What effect would stiffer springs have on a resonant frequency? Also if a vehicle that is lightly damped passing over a bump at a certain speed, its chassis bounced violently. I know this is because the resonant frequency is equal to the applied frequency. Does constructive interference play a part for the huge increase in amplitude? 3) What effect would it have on the resonant frequency of the vehicle is traveling at a different speed? 4) What effect would it have on the resonant frequency if more passengers were in the car? Thanks, I just need some explanations so I can understand this.