Test 2- Part 1: Biomechanics Flashcards
Study of physical actions of forces
Mechanics
What two systems are mechanics divided into?
Statics & Dynamics
Study of systems that are in a constant state of motion, whether at rest w/ no motion or moving at a constant velocity w/out acceleration
Statics
Study of systems in motion with acceleration
Dynamics
This involves all forces acting on the body being in balance resulting in the body being in equilibrium
Statics
Description of motion and includes consideration of time, displacement, velocity, accleration, and space factors of a system’s motion
Kinematics
Study of forces associated w/ the motion of the body
Kinetics
Load/effort =
Mechanical advantage
Using relatively small force (of effort) to move a much greater resistance
Mechanical advantage
Used to increase mechanical advantage
Machines
What are the four ways in which machines function?
- Balance multiple forces
- Enhances force in an attempt to reduce total force needed to overcome a resistance
- Enhance ROM & speed of movement so that resistance may be moved further or faster than applied force
- Alter resulting direction of the applied force
The musculoskeletel system provides 3 types of machines, what are they?
Levers (most common)
Wheel-Axis
Pulleys
Which machines are not found in the body?
Inclined plane
Screw
Wedge
A rigid bar that turns about an axis of rotation or a fulcrum
Lever
Point of rotation about which lever moves
Axis
In an arm, what represents the bars, axes, and applied force of a lever?
Bicep- force
Joint- axis
Bones- bars
All levers consist of what?
Axis (fulcrum)
Force (effort)
Load (resistance)
Axis between force &/or resistance
1st class lever
A F R
3rd class lever
A R F
2nd class lever
First class levers produce:
Balanced movements
Speed & ROM
Source motion
When does a first class lever produce speed & ROM?
When the axis is close to force (triceps in elbow extension)
When does first class levers produce source motion?
When axis is close to resistance (crowbar)
Where is force applied?
Where muscle inserts in bone (NOT BELLY OF MUSCLE)
Produces force movements, since a large resistance can be moved by a relatively small force
Second class levers
What are some examples of SCL?
Wheelbarrow
Nutcracker
Loosening a lug nut
Raising body on toes
Produces speed & ROM movements; the most common in humans. Requires a great deal of force to move even a small resistance
Third class levers (shoveling)
The turning effect of an eccentric force (moment of force)
Torque
Force applied off center or in a direction not in line with the center of rotation of an object w/ a fixed axis. Must occur for rotation to occur
Eccentric force
Equation for torque
Force x Force Arm = torque
Perpendicular distance between location of force application & axis
AKA?
Force arm
Moment arm & torque arm
How can you increase torque to help more easily move a relatively large resistance?
Increase force arm length
Distance between the axis and the point of resistance application
Resistance arm
Longer the force arm, the _______ ________ required to move the lever if the resistance & resistance arm stay constant
Less force
Shortening the resistance arm allows a __________ ____________ to be moved if force and force arm remain constant
Greater resistance
There is an inverse relationship between _______________________ and a proportional relationship between ______________________.
Length of the two lever arms
Force components & resistance components
Greater resistance or resistance arm requires what?
Greater force or a longer force arm
In a FCL, if the axis is right in the middle of the force arm and resistance arm, how much weight is needed to balance it?
An equal force
In a FCL, if the force arm becomes longer __ _____________ ________ of force is required to move a relatively larger resistance
A Decreasing amount
As the force arm becomes shorter, __ _____________ _________ of force is required to move a relatively smaller resistance
An increasing amount
In SCL, placing the reistance halfway between the axis & the point of force application provides a MA of:
2
In a SCL, what happens if you are to move the resistance closer to the axis?
The MA increases, but decreases the distance that the resistance is moved
In a SCL, what happens if you are to move the resistance closer to the force?
The less of a MA, but the greater the distance it is moved
In a TCL, a force greater than the resistance….
is ALWAYS required due to the resistance arm always being longer
In a TCL, what happens when the force application is closer to the axis?
There is an increase in the ROM & speed
In a TCL, what happens when when the force application is closer to the resistance?
It decreases the force that is needed
What do short fore arms & long resistance arms require in order to produce movement?
Great muscular force
The longer a lever is, the more effective it is in imparting __________
Velocity
For ______________, it is more desirable to have a short lever arm.
Quickness
Used primarily to enhance ROM & speed of movement in the musculoskeletal system
Wheel and axles
The center of the wheel & the axle both correspond to the ________
Fulcrum (axis)
If the wheel radius is __________ than the radius of the axle, then, due to the longer force arm, the wheel has a ____________ ______________ over the axis
Greater
Mechanical advantage
If application of force is reversed and applied to the axle, then the mechanical advantage results from the wheel
turning a _________________________
Greater distance & speed
Function to chance effective direction of force application
Single pulleys
Lateral malleolus. As peroneus longus contracts, it pulls toward it’s bell (toward the knee). Using the lateral malleolus as a pulley, force is transmitted to plantar aspect of foot resulting in eversion/plantarflexion
Pulley example
