Velocity, Displacement & Acceleration: Science vs. Engineering

One often encounters the question: What is the difference between science and engineering? An oft quoted answer is that engineering involves, roughly speaking, an application of science or scientific results borne out of investigation into the nature of matter and its interaction with its surroundings. Science is about acquiring more knowledge and understanding about existing phenomena whereas engineering involves solving problems by applying that knowledge. Therefore, many also hold the view that it is applied science. Well, I won’t get into the debate of engineering vs. science or put before you an essay on this topic in this post. I would just like to highlight an example of where engineering takes over from science. Every student studies the concepts of velocity, acceleration and displacement in elementary Physics classes. These concepts are very simple: velocity is the derivative of displacement with respect to time while acceleration is the derivative of velocity with respect to time. Therefore to get displacement from velocity , one needs to integrate the former with respect to time over a given time period. Similarly, velocity at a certain point in time is the result of integration of acceleration over a given time interval. Now, if one is asked to apply these principles to calculate velocity and displacement using the acceleration data obtained from a transducer mounted on an engine, how would one do it? In this case, the engine vibrates and there is no physical noticeable movement of engine body from one place to another in the traditional sense (like a ball traveling from place A to place B in a field). This is where engineering comes in. An engine is a complex system and its vibrations need not be linear or constant in time. There can be vibrations with low frequencies as well as high frequencies and there can be periods of no vibration at all. In these cases, calculation of displacement or velocity is not straight forward and requires greater insight into the mechanism of vibration as well as the nature of acceleration signal. I would recommend reading up 1, 2 and 3 to get an idea of how interesting and insightful it can become! These are links to articles by Prosig  which works in the area of noise and vibration analysis. Understanding these mechanisms is important for any embedded designer who writes code to measure such parameters using microcontrollers etc.