Dynamics are an extremely powerful feature in any 3D application.
Without them there would be no particle effects like smoke and fire or complex cloth simulations.
Dynamics are a complex physics engine inside the 3D application; dynamics describes how objects move using rules of physics to simulate real-world forces.
Dynamics are vital for creating realistic motion that would otherwise be extremely difficult and time consuming to achieve with traditional keyframe animation.
Without dynamics most of the jaw-dropping 3D effects we see wouldn’t be possible.
They are a type of animation simulation but they differ in how they are calculated in the computer.
Typically dynamics are calculated from frame to frame, and the position of an object in each frame is taken from the position of the previous frame.
Dynamics have the ability to quickly and easily simulate this type of animation with what is called a rigid body, whether it’s a line of dominoes falling or a wrecking ball demolishing a brick wall.
Most 3D applications have built-in effects great for quickly dropping down an effect that will produce very nice results.
One of the most powerful features in a dynamics system is particles.
While the built-in effects that come in most 3D applications are great, particles allow us to fine tune the effects and have complete control over our dynamic simulation.
Unlike the built-in effects, particles do not produce the desired look right at the start, and will need to be adjusted to create the look of the effect that you want.
What to Expect When Working With DynamicsWhen working with dynamics there is inevitably going to be a significant amount of trial and error.
Even with pre-made effects like the fire effects, there will most likely be editing that needs to be done in the effect’s attributes, in order to get exactly what you are looking for.
When working with dynamics, the typical workflow is tweak and test.
When played back, complex dynamics can give undesirable results or be slow all together, because the computer has to calculate everything on the fly.
(text from blog.digitaltutors.com)