Biomechanics Flashcards
What is kinematics vs kinetics
Kinematics = analysis of movement
Kinetics = analysis of force
What plane is the frontal axis perpendicular to?
Sagittal plane
Terms for:
- Movement in one dimension
- In two dimensions
- Motion about an axis
- Movement involving a combination of the above
- Rectilinear motion
- Curvilinear motion
- Angular or rotational motion
- General motion
What is the unit of torque?
N/m
What is moment of inertia?
The resistance to angular movement (rotation) - angular equivalent to mass
Conversion degrees to radians
360 degrees = 2 pi radians
What is graphical differentiation?
Drawing a tangent to the curve and calculating the gradient of the tangent.
what impact does errors in recording of displacement data have on calculation of velocity and acceleration using that data?
What kind of technique (giving an example) is used to deal with this?
Small differences/errors are amplified.
‘Noisy’ data should be smoothed e.g. plotting a best fit graph.
If a displacement graph is concave upwards what does this mean in terms of acceleration?
Positive acceleration
What does EAUM stand for?
Equations of uniformly accelerated motion
First EUAM?
v2 = v1 + (a . t)
Second EUAM?
d = (v1 . t) + (1/2a . t^2)
Third EUAM?
d = (v2^2 - v1^2)/2a
Quadratic formula?
Formula for horizontal range (based on velocity and angle of projection)
R = V^2 . sin (2.theta)/g
Sine double angle formula
Cos theta . Sine theta = sin (2 . theta)/2
Working definition of force from a mechanical point of view?
“That which pushes or pulls either by direct contact or by action at a distance
Newton’s second law?
The acceleration of a body will be directly proportional to the force acting and the mass of that body.
F = m . a
Difference between mass and weight and how to calculate weight/units measured in
Mass is scalar vs weight which is a vector
A person with a mass of Wkg will have a weight of 9.81W N (on Earth)
Newton’s third law?
Every force has an equal in magnitude and opposite in direction reaction force
What is the equation for friction?
How is this affected by area of contact?
Friction = mu x N
where:
mu = coefficient of friction
N = normal reaction force of the body (the perpendicular force)
Unaffected by area of contact
What is static friction vs dynamic friction?
When the body remains still on the surface whilst a force is being applied - static friction
Once motion starts and the friction is overcome - dynamic friction
Newton’s first law?
Every body continues in its state of rest or uniform motion in a straight line except when it is compelled to change its state by an external force.
What is the formula for the coefficient of friction with respect to the angle of the surface to the horizontal?
Tan theta
What is the definition of a moment?
A force acting around a fixed axis
What are the names for the two forces acting in a lever system?
Resistance force
Effort force
What are the three classes of lever?
1st class - effort and resistance forces are on opposite sides of the fulcrum
2nd class - effort and resistance forces are on the same side of the fulcrum, with the resistance force between the effort force and the fulcrum
3rd class - as for 2nd class but the effort force is between the resistance force and the fulcrum
What is the formula for mechanical advantage?
MA = Effort arm distance/Resistance arm distance
What are the benefits vs disadvantages of class 3 vs class 2 levers
Disadvantage - mechanical disadvantage with force being applied closer to the fulcrum - much greater force required
Advantage - small movement of muscle required to generate large movement in lever quickly
Formula for moment?
Moment = F . d
Where:
F = Force
d = Shortest (perpendicular) distance between line of action of the force and the axis of rotation
Which direction of moment (with respect to the axis of rotation) is denoted by positive moment?
Anti-clockwise
What is the impulse momentum relationship?
F . delta (t) = delta (v) . m
What are the two commonly used methods of numerical integration and what assumptions do these both rely on?
- The Trapezium Rule
- Simpson’s rule
Both rely on the assumption that the data points are relatively close together and the shape of the curve between the two data points can be assumed to have a particular form
What form does Simpson’s rule assume exists between the relevant points
A parabolic curve exists between 3 points
What is the formula for Simpsons rule?
Area = delta (x) / 3 . (y0 + 4 . y1 + y2)
where delta (x) is the change in time between two points in the curve (y0 and y1 or y1 and y2)
