title: Warning encountered using ideal translational velocity and not ideal force source in Simscape for spring-mass-damper system
body: <p>For my project, I am planning to conduct simulations in Simulink for an investigation on viscoelasticity behaviour that 3D printed plastic coupons seem to exhibit. Viscoelastic behaviour can be represented by different spring-dashpot combinations such as the ones seen in the Maxwell or Kevin-Voigt models.</p>
  
  <p>For this purpose, I will be using Simscape elements to represent the layers of the 3D-printed object using spring, mass and dampers in the system. For my first attempt, I have used just a simple two mass system with spring-dashpot in series and observe their displacement using the scope element. For the the mechanical source, I have tried using both an ideal translational velocity source as well as an ideal force source.
  Here is my Simulink diagram:</p>
  
  <p><a href="https://i.stack.imgur.com/gS9NU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gS9NU.png" alt="Simulink Diagram with ideal translational velocity source"></a></p>
  
  <p>Initially, I tried using an ideal translational velocity source, I encountered two warnings:</p>
  
  <p><a href="https://i.stack.imgur.com/yqiIO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yqiIO.png" alt="Simulink warning box"></a></p>
  
  <p>Thus, I attempted to use an ideal force source instead as most of the examples for modelling in spring-mass-damper using Simscape that I found used that as a mechanical source instead, which managed to work. (I only changed the source from an ideal translational velocity to an ideal force source)</p>
  
  <p><a href="https://i.stack.imgur.com/X0YjC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X0YjC.png" alt="Simulink diagram with ideal force source"></a></p>
  
  <p>However for the purpose of my experiment, it would serve me better to use the ideal translational velocity source instead as the strain testing was conducted at a constant speed of 10mm/s that is to say a constant velocity rather than a constant force which would imply that the speed is changing.</p>
  
  <p>I am not sure whether the warnings obtained when using the ideal translational velocity element would affect my results and how I can deal with the warnings, would really appreciate any help I can get as I am super new to Simulink! :)</p>