Levers

Question 1

Levers

Answer 1

A lever is a rigid bar that runs about an axis of rotation called a fulcrum. Having an understanding of levers is important because the rigid bar represents our bones and the fulcrum is the joints. The muscle contractions represent force.

Question 2

Parts of a lever

Answer 2

Effort arm: the portion of the lever arm between the applied effort and the axis

Lever arm: the rigid bar portion of a lever that rotates around the fulcrum

Resistance arm: the portion of the lever arm between the load and the axis

Moment arm: the perpendicular distance between the fulcrum and the line of the force being applied

Question 3

Types of levers

Answer 3

First class
The fulcrum (axis) is located between the effort and the load (resistance).

Seesaw

Extension and flexion of the neck, with the fulcrum at the base of the skull

Second class
Load (resistance) is located between the fulcrum (axis) and the effort.

Wheelbarrow
Few instances of this type of lever can be found in the body.

Plantar flexion of the foot used to raise up to the toes, with the ball of the foot acting as the fulcrum

Third class
The effort is between the fulcrum (axis) and the load (resistance).

Shoveling
Most levers in the human body are of the third class.

Elbow flexion driven by the biceps brachii, with the elbow joint acting as the fulcrum