Sean Walton
ex physics student, ex physics teacher, current research engineer at Swansea University
A Physics Toolbox
http://slides.com/seanwalton/physicstoolbox
What is a Force?
Discovery or invention?
Force is a tool we can use to predict motion
(...which includes deformation)
Free body diagrams
These are diagrams used to identify and simplify the forces acting on something...
Free Body Diagrams
...a tool to simplify complex systems into a few resultant forces
Newtons Second Law
The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed
The change of momentum of a body is proportional to the impulse impressed on the body, and happens along the straight line on which that impulse is impressed
Moments
Moments
...take into account the position of forces
...tell us if something is going to rotate
How do we figure out where gravity acts from on a complex shape?
So...
- Free body diagrams show us the forces (we need to find the CoM to do this, and we need to identify any moments in the system)
- Forces (with mass) give us the acceleration
- Acceleration allows us to predict the motion using...
Equations of Linear Motion (or SUVATs)
Linear Motion means constant acceleration - this is our assumption we always need to keep this in mind!
- s = displacement
- u = initial velocity
- v = final velocity
- a = acceleration
- t = time
Aerodynamic Forces
Lift = Coefficient of Lift x (Density of Air / 2) x Wing area x Velocity x Velocity
Drag = Coefficient of Drag x (Density of Air / 2) x Wing area x Velocity x Velocity
Aerodynamic Coefficients
Usually the coefficients are found either from experiment or simulation
Lift Curves
...the drag force changes with velocity so acceleration is not constant
A Physics Toolbox
By Sean Walton
A Physics Toolbox
In this lecture we will discuss some basic tools from physics which will help your design process.
