Attendance
Hardware Hack-day
Midterm project workshop
- Presentations: 5-7 minutes with 2-4 minutes for questions
- Start with an intro of the idea and why you chose to make it (this addresses the function)
- Explain how it works (or should work...)
- Demonstration
Artist Spotlight: Kal Spelletich
"Save the world. Everything is subject to change and probably will."
Statics
- The study of rigid bodies that are in equilibrium
- Equilibrium = “a state of rest or balance due to the equal action of opposing forces” (dictionary.com)
- Why study things that don’t move in a class about how things move?
- A static problem is a snapshot of a dynamic one
- Most of the time we can isolate a statics problem that represents the worst case scenario in a dynamic system
Force as a vector
What’s a vector?
- Scalar: speed, mass, length, time
- Vector: velocity, weight
When describing a force, think of
- Point of application (simplify)
- Magnitude
- Direction
Gravity is a force F=ma (Newton's 2nd law)
Difference between mass and weight
Quick Trigonometry lesson
Free Body Diagrams (FBD)
- A FBD is a simplified graphical depiction of all the forces and moments happening on a body
- Applied, normal, friction, weight, gravity, spring, drag, etc.
- Examples:
- Book on a table (Newton’s 3rd law - Every action has an equal and opposite reaction)
- Hanging from two ropes
- Weight on a high crane
- 3 steps
- Isolate the body from all supports
- Identify all external forces acting on the body
- Sketch the body, showing all forces
Solving a Statics problem:
- Draw a FBD
- Choose a reference frame (x horizontal, y vertical)
- Choose a convenient point to calculate moments around
- Sum forces and moments in all directions until unknowns are found
Torque and FBD
- We already learned that Torque (moment)=Force*distance
- Distance (d) stands for the PERPENDICULAR distance between the force line of action and the point of rotation, sometimes called the lever arm or moment arm
- For something to be in Static Equilibrium, the sum of forces in any direction and the sum of moments about any point must = 0