Dynamics. The field of dynamics uses the knowledge of classical mechanics that is concerned with effects of forces on motion of objects. Engineers use the concepts in design of any moving parts, such as for engines, machinery and motors. For example, a mechanical engineer would have used Dynamics extensively in the design of the pneumatically powered, multirow seed planter that was invented in 1956.

Dynamics – the study of forces and torques and their effect on motion. Dynamics is mostly related to Newton’s second law of motion. Dynamics falls under two categories: linear and rotational.

- Linear dynamics – objects moving in a line – force, mass/inertia, displacement, velocity (distance per unit time), acceleration and momentum
- Rotational dynamics – objects that are rotating or moving in a curved path – angular displacement, angular velocity, angular acceleration and angular momentum

Engineers often design devices that transport fluids, use fluids for lubrication, or operate in environments that contain fluids, such as engines, printers and pacemakers. It is important for engineers to understand how fluids behave under various conditions.

Engineering Mechanics (Dynamics)

- Introduction to Dynamics. history, applications, definitions, units and dimensions, Newton’s laws
- Kinematics of Particles. planar motion (rectilinear, curvilinear), coordinate systems (rectangular, normal and tangential, polar), conversions between coordinate systems, 3D motion and coordinate systems (rectangular, cylindrical, spherical), free and constrained paths, relative motion between particles
- Plane Kinematics of Rigid Bodies. motion (displacement, velocity and acceleration) in 2D using vector analysis, scalar algebra and graphical approach: translation (rectilinear and curvilinear), fixed-axis rotation, general plane motion, absolute and relative motions, motion relative to rotating axes
- Kinetics of Systems of Particles. generalized Newton’s Second Law, work and energy, impulse and momentum, conservation of energy and momentum, impact

**Go with the flow**

Fluid dynamics at the Olympics (video) Missy Franklin masters the basic principles of fluid dynamics to become the fastest Olympic swimmer.

Understanding fluid behavior can help engineers to select the best fluid to operate in a device or to design devices that are able to efficiently and harmlessly operate in environments that contain fluids. Questions correspond to the steps in the Engineering Design Process.

- What factors affect the swimmers performance? How does the water in the pool slow the swimmer?
- How can the water flow be modified? What would reduce the turbulence from swimmers?
- What changes are incorporated in the pool overflow?
- How do the lane lines dissipate turbulence?
- How can changes to swimmers’ suits improve their performance?

**Engineering ideas**

- Newtonian fluid, viscosity, aerodynamics, mechanics, vectors, coordinate systems, motion, Newton’s 2nd Law, momentum principle, rigid bodies, fluids, pivots, springs, weights, change elasticity, friction, inertia, torque, angular velocity.

**Do it**

Here are some challenges for you to work on…

- iDynamic (app – free) – concepts of system dynamics and modeling. It implements the animated and iterative simulation of some common dynamical systems. In all the simulations, the main parameters of the system can be changed (for example in the mechanical system, change the mass of the object). All the systems are modeled as input-output systems (plants) so they all have a variable as input and a variable as output.
- PhyDios (game-based learning, app, free) – rigid bodies, fluids, pivots, springs, ropes, rods, layers, motors, magnet. connect bodies using spring, rope, rod, or pivot. Physics Properties – weights, change elasticity, friction, inertia, torque, angular velocity.

- Surface tension – a liquid’s tendency to either bead or sheet on a solid surface is determined by the properties of both the surface and the liquid.

**Learn more…**

- Viscous fluids
- Missy Franklin – swimmer video – thrust, drag
- Chemical Process Dynamics and Controls = open textbook – Modeling Basics, Sensors and Actuators, Piping and Instrumentation Diagrams, Logical Modeling
- Engineering Mechanics: Dynamics