Differentiate Kinetics and Kinematics

Kinetics and kinematics is a pair of terms that is often confusing. Whenever we come across the words like these get very puzzled as to which one is right or even if both are right which one is more appropriate to use within the given context. Some brilliant minds think it as a dilemma between American and British English without even googling it!!! Well, let me just tell you – this is not the case.  Let’s try to find out the actual difference between kinetics and kinematics and fix this mix-up once and for all.

“Mechanics” is the one umbrella term that includes two branches namely, “statics” and “dynamics”, and dynamics are further divided into two sub-branches called “kinetics” and “kinematics”.  (boom!)

I hope you’ve got the idea that kinetics and kinematics are not synonymous. Now, let’s dig a little deeper and briefly see what these highlighted terms mean. (cause it’s worth it!)

What is Mechanics?

Mechanics is a branch of physics concerned with the study of an object under the influence of an external quantity. This external quantity can be a force, a torque (a twisting force) or momentum. 

What is Statics?

Statics is the division of mechanics which deals with a body in equilibrium and when I say equilibrium, I mean the body is either at rest or in uniform motion i.e. moving with a constant velocity.

What is Dynamics?

Dynamics deals with the objects under accelerated motion due to the effect of a force. The key difference between statics and dynamics is that there is no acceleration in statics. The dynamics of a body consider its motion and the underlying reason behind motion e.g. the force.

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What is Kinematics?

Kinematics is concerned with the study of the motion of a point, a body or a system of bodies without bearing in mind the cause of motion i.e., force. (kinematics does not take into account the body’s mass also because that would mean taking force into account indirectly, REMEMBER   F= m*a ). Hence, we can say that while dealing with the kinematics of a body we are interested in pure motion only. Kinematics is not curious about “how the change?” but “how much change?”

In order to describe the motion of a body we put into service the following well-known equations, therefore, these equations are better known as kinematic equations and not kinetic equations.

Kinematic equations

 v=u+a t  [velocity-time relation]

s=u t+\frac{1}{2} a t^{2} [position-time relation]

 v^{2}=u^{2}+2 a s [position-velocity relation]

here –

• symbol v stands for final velocity
• symbol u stands for initial velocity
• symbol a stands for acceleration
• symbol s stands for displacement
• symbol t stands for time as a reference

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Given its mathematical niche kinematics is also considered another branch of mathematics.

Kinematics is often referred to as geometry of motion for it focuses on the geometrical aspects of the motion.

What is Kinetics?

Kinetics is a vast field as it used not only in physics but also in chemistry and biology. In pure physics terms, it talks about the motion of a body taking into account the cause of motion. In kinetics the cause of motion (force) is studied extensively, this is the key difference between kinematics and kinetics. Newton’s laws of motion are employed extensively in kinetics. In terms of chemistry, it gives the rate of a chemical reaction. Kinetics is used in biology in terms of enzyme kinetics as to how an enzyme affects the rate of a biochemical reaction.

You may find in some text that the term kinetics is suppressed by the term dynamics and this has been done to eliminate the ambiguity between the two terms. Now, as you know the difference between kinetics and kinematics clearly, this ambiguity should not exist.