Week 2- Levers and Mechanical Advantage Flashcards
Lever
A simple machine consisting of a rigid rod suspended across a pivot point or axis
Lever system
when two forces are applied to a lever in a way that produces opposing torques
Moment Arm
distance from the Axis (Fulcrum) to the location of force
Components of a lever
- Effort Force (EF)
- Resistance Force (RF)
- Effort Arm (EA)
- Resistance Arm (RA)
Effort Force (EF)
Force producing the resultant torque
Resistance Force (RF)
Force creating an opposing torque
Effort Arm (EA)
Moment Arm (distance from axis to location on force) of the effort force
Resistance Arm (RA)
Moment Arm for the resistance force
Classes of levers
- Class 1
- Class 2
- Class 3
Class 1 Lever
Fulcrum is between effort force and resistance force
Class 2 Lever
The resistance force is between the fulcrum and the effort force
Class 3 Lever
The effort force is between the fulcrum and the resistance force
Mechanical Advantage
- Measure of mechanical efficiency of a lever system
- MA = EA/RA
Mechanical advantage of a Class 1 Lever
Mechanical advantage can
vary
Mechanical advantage of a Class 2 Lever
Mechanical advantage
greater than 1
Mechanical advantage of a Class 3 Lever
Mechanical advantage less
than 1
What happens to the class of a lever when the exercise is closed chain vs open chain?
It can change depending on if its open or closed chain
Limitations of lever systems in the body
- Ignore the fact that rotation of a level requires at least one force couple to help stabilize the at least on part of the lever system
- Torques on the human body are not simply produced by muscle and external forces
Factors that can maximize torque
- Increase the magnitude of the force
- Applying the force perpendicular to the lever
- Increasing the distance of the point of application of the force from the joint axis
