Please explain the relevance of the shock absorber and the springs in a car's suspension. I have been told that springs absorb shock, so what is the purpose of the "shock absorber"? And how does it affect my car's safety and performance?
The term "shock absorber" is often used incorrectly. In a car's suspension system, whenever a wheel encounters a surface irregularity, the element of shock is absorbed by the spring. This is applicable to any mechanical system.
Springs, while having the ability to return the wheel to its original location, have the natural tendency to extend a little further than necessary, which means the vehicle might bounce a few times before settling down.
This is where the "shock absorber" comes into play. The proper name for it is "damper" as it serves to dampen motion.
While shock is absorbed by the spring, the damper functions to modulate the oscillations (bouncing).
The unique feature of a damper is that its resistance to motion is proportional to how fast the motion occurs. Try moving your palm against the water in a bathtub or swimming pool. Clearly, it takes less effort to do so if you move slowly than when you try to sweep quickly.
This analogy applies to a car's set of dampers.
Dampers have a much harder life and experience greater wear than springs. Hence, they would require periodic replacement.