Biomechanics Flashcards
What are the two most important principles in kinesiology?
Mobility and stability
What are the four aspects of kinesiology?
Mechanical (biomechanics), neural (motor control), cardiovascular, and psychological
What is the relationship between mobility and stability?
When a joint is stable, it has less mobility and vice versa
What is the definition of biomechanics?
The study of mechanics applied to posture and movement
What are the two areas of study of biomechanics?
Statics and dynamics
What is the sum of the forces when something is static?
Zero
What is the equation for torque/moment?
Torque/moment = moment arm x force
When do you apply the least amount of force in regards to the moment arm and pushing a door?
You apply the least amount of force when the moment arm is the longest
What is the difference between kinematics and kinetics?
Kinematics - the study of just motion (ex: gait and normal ROM)
Kinetics - the study of motion with force (ex: muscles active in different exercises)
What is displacement?
The change in position over time
What are the five kinematic variables to describe displacement?
Type (motion), location in space, direction of displaced segment, magnitude, and rate of change in displacement (velocity) or the rate of change of velocity (acceleration)
What are the three types of displacement?
Translatory motion, rotary motion, and general (curvilinear) motion
What is translatory motion?
Occurs when each point of a segment moves through the same distance at the same time - aka linear displacement
What is general (curvilinear) motion?
The combination of linear and rotary motion - object is rotating around an axis while also being translated
What type of motion is most common in humans?
General (curvilinear) motion
Where does the axis of rotation occur in relation to the plane of motion?
Perpendicular
What plane is related to the x-axis?
Sagittal plane
What plane is related to the y-axis?
Transverse plane
What plane is related to the z-axis?
Frontal (coronal) plane
What are the options of movement of a segment referred to as?
Degrees of freedom
What are the two types of magnitudes of motion?
Angular motion - range of motion
Translatory motion - distance
What is speed?
Displacement per unit time regardless of direction
What is velocity?
Distance travelled in a unit of time given direction
What is acceleration?
The change in velocity per unit of time
What is the equation for force?
Force = mass x acceleration
What is the cause an effect relationship between a motion and a force?
Every motion is caused by a force, but a force does not always cause a motion
What do you need in order to apply a force?
A physical contact
What are the four components of force vectors?
Magnitude, direction, line of action, and point of application
What are vector quantities?
All forces acting on an object
What is torque/moment?
The force acting to rotate a body around an axis
What two things is the effect of a rotary force dependent on?
Magnitude of the force and its moment arm
What is the moment arm (lever arm)?
The perpendicular distance from the line of action to the axis of rotation
What is the center of gravity?
The point at which the total mass of a body is in balance in all planes
When an object is symmetrical, where is the COG located?
In the center of the object
When the object is asymmetrical, where is the COG?
Towards the heavier side of the object
Where is the center of mass in relation to the vertebral column?
S2
What happens when the COG moves over the base of support?
The body will not be able to stand
What are some things that affect stability?
Base of support, placement of the line of gravity relative to the base of support, height of the COG, and the mass of the object
What is Newton’s 1st Law?
A body stays at rest or in uniform motion unless acted upon by an unbalanced or outside set of forces
What is inertia?
The resistance of an object to motion or change in motion
What two types of motion does inertia apply to?
Linear motion and rotary motion
Regarding linear motion, what is inertia dependent on?
Mass of the object
Regarding rotary motion, what is inertia dependent on?
Mass of the object and the distance of the mass from the axis of motion (the closer the mass, the less the inertia)
What is Newton’s 2nd Law?
When a force acts on an object, the object accelerates in direct proportion to the magnitude of the force applied and in inverse proportion to its mass
What is Newton’s 3rd Law?
For every action, there is an equal and opposite reaction
What is a linear force system?
When two or more forces act on the same segment in the same plane and in the same line, the forces can be added together and result in a single resultant vector
What is a concurrent force system?
When two or more forces meet at a common intersection but their action lines differ, a resultant force is created - forces in two different directions equal a resultant force
What happens when the force is at 90 degrees?
All of the forces are going in the downward direction
What are the two types of force components and how are they applied in relation to a segment?
- Rotary component (Fy) - perpendicular to the segment
2. Translatory component (Fx) - parallel to the segment
What is a parallel force system?
Occurs when two parallel forces are acting on the same object at different locations
What is a general force system?
A force system that does not fit in the three categories of force systems (concurrent force system, linear force system, or parallel force system)
What is a first class lever system?
When the axis is between the force line (effort force) and the resistance line (resistance force)
Which force always wins and which always loses?
Effort force = always wins
Resistance force = always loses
What is a second class lever?
When the resistance line if between the force line and the axis
What is a third class lever system?
When the force line is between the resistance line and the axis
What is the equation for mechanical advantage?
MA = force (effort) arm / resistance arm
When is a system considered inefficient and efficient and which levers are which?
1 = efficient
1st - depends
2nd - good
3rd - poor
What is friction?
The force created between two contacting surfaces that tend to rub or slide past one another
What are four things that the magnitude of friction depends on?
Texture of the surfaces, how much force is pressing the two surfaces together, whether friction prevents or resists the motion, and at what time the object moves
When is friction the greatest?
Right before it moves
What is the idea behind tensile forces?
The more we pull, the more resistance is created
What is a mechanical advantage of third class levers?
Increased ROM
What is a force couple?
When two or more forces creates a single motion
What is work and what is the equation?
A transfer of energy resulting in motion or displacement
W = force x distance
What is negative and positive work?
Positive = force and movement in the same direction Negative = force and movement in opposite directions
What is energy?
The capacity of a body to perform work
What are the two types of energy?
Kinetic energy - energy of motion
Potential energy - stored energy
What is power and what is the equation?
Rate of work production
P = work / time
What are closed kinetic chain exercises?
When both ends of the segments are constrained - two or more joints are affected
What are open kinetic chain exercises?
When the distal end of the segment is free to move in open space
What is rotary motion?
Occurs when the segment moves in a curved path around a fixed axis - aka angular displacement
