week 9 biomechanics Flashcards
exam 2, revision
What are the basic kinematic variables in linear motion?
Displacement (m), Velocity (m/sec), Acceleration (m/sec²)
What are the equivalent kinematic variables in angular motion?
Angular Displacement (degrees or radians), Angular Velocity (°/sec or rad/sec), Angular Acceleration (°/sec² or rad/sec²)
What forms an angle in angular displacement?
Two lines, Two planes, One line and one plane
What is absolute angular position?
When the other line or plane is fixed, such as the angle of the trunk with the horizontal.
What is relative angular position?
When the other line or plane is capable of moving, such as the angle of the thigh with the shank.
What are common units of measure for angular displacement?
Degrees and radians (rad)
How are radians defined?
Radians are a measure of the length of an arc divided by the radius of the circle.
What is the relationship between radians and degrees?
2 π rad = 360°, OR rad = 57.3°
What is the difference between angular displacement and angular distance?
Angular displacement is a vector, while angular distance is a scalar.
How is the direction of angular displacement determined?
Clockwise displacement is considered negative, and anticlockwise displacement is positive.
How is angular velocity calculated?
Angular velocity = change in angular displacement/change in time
What are the units for angular speed and velocity?
Degrees per second (°/sec) OR rad/sec
What is angular acceleration?
Angular acceleration = change in angular velocity/change in time
What is a concentric force?
A force whose line of action passes through the CoG of the body on which it acts.
What is an eccentric force?
A force whose line of action does not pass through the CoG of the body on which it acts.
What is torque?
The turning effect produced by a force, calculated as T = F . d.
What does ‘d’ represent in the torque equation?
‘d’ is the perpendicular distance from the axis of rotation, also called the moment arm.
How can torque increase?
By increasing the magnitude of force or increasing the perpendicular distance from the axis of rotation.
Why are door handles located on the opposite side from the hinges?
To maximize efficiency when opening doors.
What factors affect torque?
The point of force application and the line of action of the force.
How do body limbs rotate?
Body limbs rotate around joints, generated by torques applied by the muscles.
What factors determine the torque generated by a muscle?
Max force the muscle can produce and tendon insertion into the bone (radius).
Why is large muscle force needed to overcome small resistance?
The moment arm of the muscle is much smaller than the moment arm of the resistance.
How much muscle force is needed to hold a 10kg dumbbell at a 90° elbow?
The required muscle force is 784.8N.
