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Dynamics is one of the areas of the mechanics, where mechanics is study of a physical body that is subjected to forces.  That physical body can be at rest or it could be in motion.  Dynamics is the study of the physical body where the forces are not in equilibrium, which in turn would cause an acceleration on that body.  On the other hand, if the body is at rest, or has constant velocity, causing all applied forces to be in equilibrium, than Statics would be used.

Dynamics can be presented in two parts: kinematic, which studies the geometric aspect of motion, and kinetics, which studies the forces that are responsible for the motion.  These areas will be discussed in further detail in other articles.

The study of Dynamics began when it was possible to produce and accurate measurement of time.  Galileo was one of the first to contribute to the field of dynamics when he was studying pendulums and falling bodies.  Isaac Newton was also major contributor to the field of Dynamics when he created the three laws of motion.  The three laws can be seen below.

  1. “Every object in state of uniform motion tends to remain in that state of motion unless an external force is applied to it.”
  2. “The relation between an object’s mass m, its acceleration a, and the applied force F is F=ma, where acceleration and force are vectors, and the direction of the force vector is the in the same direction as the acceleration vector.”
  3. “For every action there is an equal and opposite reaction.”

The first law was actually developed by Galileo’s concept of inertia and due to this fact it is called the “Law of Inertia.”  A perfect example of this would be an object in outer space.  Any object in space will continue to move at a constant speed unless an external force acting on that object changes its speed.

The second law, which is one of the most important law of motion, is used to determine the resultant forces due to a certain acceleration on an object.  This law is the basis of Kinetics.

Finally, the third law states that if an object acts on another object than it action on that object will have an equal and opposite reaction on itself.  For example when you step off of a boat that is docked, that boat will move away from you as you step towards that dock.

So why is dynamics important to a mechanical engineer?  Simply, it is important to a mechanical engineer because most mechanical systems have motion, which means there are chances of acceleration which can cause a force.  Those dynamic forces can in turn causes stresses on the object.  They can also upset the balance of the object.  Due to these facts it is important for a mechanical engineer to have firm understanding of Dynamics.

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