Basic Mechanical Principles Flashcards
What is a force?
- An action of one body acting on another
- A push or pull on a system
What are forces characterized by?
- Magnitude (lbs)
- Location
- Direction
- Duration
- Frequency
- Rate
What are common forces that act upon the human body? What is each?
- Gravity: pull of Earth of an object; the “weight”
- Externally applied resistance: outside forces acting on the body; weight or people
- Friction: resistance to movement
- Muscles: internal force that inhibits torque and rotation of joints
What are force vectors? What factors do they represent?
- Arrows that represent forces
- Magnitude (length of arrow)
- Direction
- Point of application
- Line of application
What is a free body diagram? What does it show?
- A pictorial representation of all forces of an object
- When you line them up end to end, it shows how the forces added together will move the object (if at all)
What is Newton’s 1st Law?
-* “Law of inertia”
- Objects in motion remain in the same motion until acted upon by an outside force
- Objects at rest remain at rest until acted on by an outside force
What is Newton’s 2nd Law?
“Law of acceleration”
- An object will accelerate in the direction of the force applied to it
- Magnitude of acceleration will be proportional to the force applied and inversely proportional to its mass
What is Newton’s 3rd Law?
Law of action and reaction”
- Every action has an equal and opposite reaction
What are the six parts of a lever? What is each? What is an example of the human body for each?
- Axis / fulcrum = pivot point (joint)
- Lever = rigid bar (bones)
- Resistance (load) force = force trying to overcome (weight)
- Resistance arm = lever from resistance to fulcrum
- Effort (moving) force = force against resistance (muscles)
- Force (effort) arm = lever from effort to fulcrum
What is a first class lever? What is an example from the body?
- Axis / fulcrum lies in between the 2 forces
- Triceps extension
- Anything with the head
What is a second class lever? What is an example from the body?
- RESISTANCE / LOAD is in the middle of the effort and fulcrum
- Calf raise
What is a third class lever? What is an example from the body?
- EFFORT is in the middle of the fulcrum and load
- Almost every action in the body
How do can I remember which class lever is which?
- The acronym: FREe
- F = first letter = first class = fulcrum in the middle
- R = second letter = second class = resistance in the middle
- E = third letter = third class = effort in the middle
“Effort creates the force, which creates movement.”
Indeed it does
When talking about body weight as being resistance, where does the resistance come from?
The center of mass of the body or objec
