Levers

lever

rigid bar that moves

fulcrum

a fixed point

effort

applied froce

load

resistance

bones

act as levers

joints

acts as fulcrums

muscle contraction

provides effort (applies force where muscle attaches to bone)

Load

bone, overlying tissue and anything lifted

Levers allow a given effort to

move a heavier load and move a load farther

mechanical advantage

moves a large load over small distances

mechanical disadvantage

allows a load to be moved over a large distance

first class lever

• effort applied at one end

• load is at the opposite end

• fulcrum is located between load and effort

examples first class levers

seesaws, scissors, lifting your head off your chest

second-class levers

• effort applied at one end

• fulcrum is at the opposite end

• load is between the effort and fulcrum

• - Work at a mechanical advantage

examples second-class levers

wheelbarrow or standing on tiptoe

(uncommon type in the body)

Third-class lever

effort is applied between the load and the fulcrum

Example third-class levers

most skeletal muscles

Biceps brachii fulcrum

the elbow joint

Biceps brachii force

exerted on the proximal region of the radius

Biceps brachii load

distal part of the forearm