Chapter 14.1, Problem 13SSC

To determine

The reason for car shaking strongly at a specific speed but not at a lower or higher speed if its wheel is out of balance.

Answer to Problem 13SSC

At a specific speed, the car’s wheel rotation frequency matches to the car’s resonant frequency.

Explanation of Solution

Introduction:

Resonance is the phenomenon of increased amplitude which occurs at the time when frequency of periodically applied load is equal to the natural frequency of the system.

At a certain speed, the rotation frequency of the car’s wheel matches the car’s resonance frequency.

For example, when thinking of pushingthe friend on a swing, if the personpushes at regular intervals at the proper time, friend will swing higher and even high. The wheel of the car which is rotating is off balance already, so when the car pushes, wheel at certain times (or speeds) then the wheel will vibrate (resonance).

Conclusion:

At a certain speed, the rotation frequency of wheel of the car matches the resonant frequency.