How do shock absorbers absorb shock?

Cars absorb shock by use of their suspension system. This is made up of both the springs and shock absorbers / dampers.

The suspension system allows the wheels to move up and down separately to the car body / chassis when a car goes over a bump or pothole. When this happens the springs compress or stretch and so help resist the displacement and because of the way a spring works, the greater the displacement the more the spring resists it.

However to stop the spring "springing" back into it's original place too quickly and to prevent it vibrating and shaking the car repeatedly (which would be very uncomfortable and also make safe control of the vehicle much more difficult) they are also fitted with shock absorbers or dampers.

These are cylinders filled with a viscous fluid with a piston inside them. The piston is porous and permeable and so can pass through the fluid but the fluid resists the motion. As the velocity of the motion increases so to does the amount of resistance. This stops the spring being forced to move too quickly when hitting a bump, it also stops it rebounding to quickly afterwards and stops the spring from oscillating backwards and forwards. Essentially it dampens the movement - hence the use of the name damper.