Musculoskeletal Machines and Lever Systems

A system using parts to apply mechanical force.

Musculoskeletal System

Any given joint in the musculoskeletal system can technically be classified as an__ machine

Intrinsic Machine

A rigid object rotating around a fulcrum.

Lever System

A machine using a wheel and axle to transmit force.

Wheel-and-Axle System

A machine using ropes and wheels to change force direction.

Pulley System

Transmit Force example

Tendons transmit muscle forces to bones.

Increase Force Magnitude has the effect of

Less effort needed to move a given resistance.

How does increasing the linear distance and velocity of a (i.e resistance) force affect the the other force in a level system

Resistance moved further or faster than motive force.

How does changing the Force Direction affect the forces

Resistance moves differently than motive force direction.

Axis of rotation in a lever system.

Fulcrum

an eccentrically applied force that attempts to rotate the lever in one direction about the fulcrum

Motive Torque

an eccentrically applied force that attempts to rotate the lever in the opposite direction

Resistive Torque

The relationship between the motive force and resistive force describes the __

Mechanical Advantage

Mechanical advantage varies with the system based on the location of the ___

fulcrum

Distance from fulcrum to point of force application.

Moment Arm

Fulcrum between motive and resistive forces.

First-Class Lever

Resistive force between fulcrum and motive force.

Second-Class Lever

Motive force between fulcrum and resistive force.

Third-Class Lever

Force applied off-axis to produce torque.

Eccentric Force

Bones acting as levers in the body are examples of __ levers

Rigid Levers

The fulcrum for bone rotation.

Joint

Lever systems are classified according to the positions of the ___ , ___, and ___

fulcrum, the motive force, and the resistive force.

If the fulcrum is in the middle, then which force has the advantage? and why?

neither the motive nor resistive force has an inherent advantage because both of their moment arms are the same length.

If the fulcrum is moved farther away from the motive force, then its moment arm becomes ___ and gains a mechanical advantage.

longer

If the fulcrum is closer to the motive force, then the moment arm for the ___ force becomes longer, and the resistive force has the advantage.

resistive