Foundations of biomechanics Flashcards
Basic biomechanic principles
What is the study of kinematics?
It describes the spatial and temporal components of motion
What are the two types of kinematics?
Linear/translational and angular
What is translational motion?
Motion along a line, where all points on a body/object move the same distance, the same direction, at the same time
Does linear motion have to be in a straight line?
No, it can either be rectilinear (traditional, straight line), or curvilnear (follows a curved path)
What is angular motion?
Motion around an axis (the joints of the body)
What is general motion?
It is a combination of linear and angular motion. E.g. in cycling, the torso is in linear motion, whilst the lower limbs are in angular
How can kinematic data be collected?
Accelerometers, high-speed photographs, high-speed video/optoelectric system, digital positional data
What is an optoelectric system?
Method whereby markers are placed on relevant points of the limb to track motion. The markers emit signals which are picked up by cameras and informs them of their position in space, allowing a digitisation to be formed of the movement.
What does a Spatial Reference System show, and what method is used?
It shows the position-location of a body in space at some instant of time, typically using the Cartesian Coordinate System (both 2D and 3D)
What is a scalar measurement? Examples too.
Provides only magnitude. E.g. speed, mass
What is a vector measurement? Examples too.
Provides both magnitude and direction. E.g. velocity, acceleration, weight
What is the formula for velocity?
Displacement/time
What does running kinematics measure?
Analyses running gait by stride length and stride rate, providing speed
How does one read a velocity graph?
By the slope. +ve and -ve slopes indicate the responding velocity, whilst gradient of 0 typically indicates a change in direction
What is the first central method formula?
V xi = (xi+1 - xi-1)/2dt
What is the study of kinetics?
It is the study of the causes of motion
What is the formula for Newtons?
1N = 1kg*1.0m.s^-2 as F=ma
What are the two different types of forces (VERY GENERALISED)?
Internal and external
What are internal forces?
Forces which act within the object/system whose motion is being investigated
What are the two different typed of internal forces?
Tensile (pulling acting on the ends of an internal structure), and compressive (pushing acting on the ends of an internal structure)
What are external forces?
Forces which act on an object as a result of its interactions with the surrounding environment
What are the two different types of external force? Examples too.
Contact (e.g. friction, air/water resistance) and non-contact (e.g. gravity, magnetic)
What is Newton’s Law of Gravity?
All objects attract each other with a gravitation force that is inversely proportional to the (distance between them)^2. And is proportional to the mass of each of the two bodies
What is the value of g?
9.81N
What is the centre of gravity?
The point through which the resultant force of gravity acts on a body and entire weight of body is balanced
What is Newton’s First Law?
The Law of Inertia; the resistance of a body to a change in its motion
What is Newton’s Second Law?
The Law of Acceleration; if an object accelerate then a net external force must be acting on it
What is Newton’s Third Law?
The Law of Action-Reaction; to every action there is an equal and opposite reaction
What are co-linear forces?
Forces which have the same line of action
What are resultant forces?
The vector addition of >=2 forces
What are net forces?
The vector addition of all external forces acting on an object
What are concurrent forces?
Forces acting through the same point but on different lines
What are co-planar forces?
Any system of forces acting in the same plane
What is the formula for Force?
F = ma
Which muscle attachments move most?
The insertions, and are typically more distal to origin
What is the formula for momentum?
p = mv
What is impulse?
It represents a net external force
What is the formula for impulse?
= F*dt
How do you find the impulse from a graph?
Is the area under force-time curves
How are impulse and momentum related?
Fdt = mdv
When is static analysis used?
When acceleration of a system is 0, meaning it is at equilibrium
When is dynamic analysis used?
When acceleration is significant
What method is used in dynamic analysis?
The Newton-Euler inverse dynamics approach
