Introduction to Biomechanics (Biomechanics I) Flashcards
Define Biomechanics
The study of the structure and functions of biological systems by means of the methods of mechanics
Biomechanics is the “physics of bodily movement” involving
- Solid Mechanics
- Fluid Mechanics
- Continuum Mechanics
Define Sports Biomechanics
By understanding and applying mechanical concepts, determine the optimal way to move the body in order to achieve maximal performance and minimizing risk of injury
Define Occupational Biomechanics
The goal is to design machines in the workplace to reduce repetitive stress on workers’ spines/joints
Define Clinic Biomechanics
Clinical biomechanists analyze the mechanics of patients and provide feedback (biofeedback) to restore normal function
FUN FACT: Cellular Biomechanics also exists
Example like Breast Cancer Cell migration
Mechanics is divided into what 2 concepts?
- Statics
- Dynamics
Define Statics
- Study of systems that are in a constant state of motion, whether at rest with no motion or moving at a constant velocity without acceleration
- Involves all forces acting in EQUILIBRIUM!!!
Define Dynamics
- Study of systems in motion with acceleration
- System in acceleration is UNBALANCED due to unequal forces acting on the body.
Define Kinematics. Provide 3 examples!
- Kinematics: Study of the variables that describe or quantify motion
- Ex.) Displacement, Velocity, and Acceleration
Define Kinetics. Provide 3 examples!
- Kinetics: Study of the variables that cause or influence motion
- Ex.) Forces, Torques, and Mass
Compare Vectors and Scalars. Provide examples!
- Vectors: Both magnitude and direction
- Ex.) Displacement, Direction, Velocity, Acceleration, Momentum, Force, Lift, Drag, Thrust, and Weight
- Scalar: Only magnitude
- Ex.) Length, Area, Volume, Speed, Mass, Density, Pressure, Temperature, Energy, Entropy, Work, Power
In the formula F=ma, what quantity is scalar and which one is vector?
- Force= Vector
- Mass= Scalar
- Acceleration= Vector
Describe Force
- Vector quantity
- A physical quantity which causes or tends to cause a change in the motion or shape of a body
- A push or pull
What are 4 properties of Force?
- Magnitude: How much force is applied?
- Direction: In what direction is the force applied?
- Point of application: Each force is considered to act at one point.
- Line of Action: The line is a straight line which extends infinitely along the direction of the force.
The skeletal system is subjected to a variety of different forces so that bone is loaded in various directions. These are loads produced by gravity, weight-bearing, muscle, and external forces in what 4 concepts?
- Compression
- Tension
- Shear
- Mechanical Stress
Describe Compression
A compressive force presses the ends of the bones together and is produced by muscles, weight-bearing, gravity, or some external loading down the length of the bone
Describe Tension
- Pulling force that creates tension in the object/body
- Tends to lengthen and narrow
- Source is usually muscle
Describe Shear Stress
Arises from the force vector component parallel to the cross section
Describe Normal Stress
Arises from the force vector component perpendicular to the cross section
Define Stress
Load per cross-sectional area
Define Strain
- Deformation with respect to the original length of the material
- There is normal strain and shear strain (defined in next two cards)
Define Normal Strain
Change in Length
Define Shear Strain
Change in Angle
What is the Free-body diagram?
Stick figure drawing of the system being analyzed on which the vector representations of the external forces acting on the system are drawn
Define MASS
Is it the same anywhere in the universe?
Measure of the quantity of matter (KG)
Yes! It is the same.
Define Weight
What formula is associated with weight?
Measure of force (pull of gravity on a mass). Varies depending on gravitational pull
W=mg (mass * gravity)
Define Gravity and the value associated with it
Downward acceleration of an object due to gravity
9.8 m/sec^2
Define Centre of Mass
- An imaginary point where the total mass of the body is considered to be centered
- Balance point where the mass of athletes for instance is thought to be concentrated
Define Inertia
- Body or objects RESISTANCE to a change in motion
- A change in motion may refer to trying to start something moving, stop it moving, or change it from moving at constant speed
What is the 1st Law of Motion?
- INERTIA!!!!
- A body at rest or in uniform (linear or angular) motion will remain at rest or in motion unless acted upon by an external force or torque
- Ex.) Whiplash injuries
What is the 2nd Law of Motion?
- A force or torque acting on a body will produce an acceleration proportional to the force or torque
- Ex.) F=ma
- Ex.) T=la
What is the 3rd Law of Motion?
- For every action there is an equal and opposite reaction (torque and/or force)
- Contact forces: Ground Reaction Force (GRF)
Define Displacement
- Vector
- Length and Direction of a line joining the initial position with the final position
Compare Speed and Velocity
- Speed: Refers to how fast something is traveling. Magnitude NOT involved!
- Velocity: Both magnitude and direction. How fast something is going and in what direction they are moving.
Define Acceleration
- Defines how much an object is speeding up or slowing down
- If an object or body is in a state of constant velocity, or a state of equilibrium then the acceleration is equal to zero
- Vector quantity!
What formula is involved in Pressure? What unit is used?
- P=F/A (distribution of force over an area)
- P= Pressure
- F= Force (N)
- A= area (m^2)
- 1 Pascal = 1 N/m^2
What are the 3 Physical Principles Influencing Pulmonary Ventilation
- Air flows from areas of higher to lower pressure
- If pressure is higher on one end of the tube, then at the other end air will flow down its pressure gradient - Changes in volume result in changes in pressure
- As volume inc in closed container, pressure decreases AKA Boyle’s Law - Changes in tube diameter result in changes in resistance
- Poiseuille’s Law: Resistance to airflow is proportional to diameter of a tube raised to the fourth power
Define Viscosity
Resistance that a fluid offers to flow when subject to a shear
If the fluid is incompressible, then inertia becomes ____, and if fluid has NO friction (no slip condition) the viscosity becomes ____
- ZERO (0)
- ZERO (0)
What formula is associated with Navier Stokes
Inertia = (-)Pressure Gradient + Body Force + Viscosity
