f t r f t r 1.5” 6” forces generated on the foot while a 150 lb man is standing (on 2 legs)?...

F

T

R

F

T

R

1.5” 6”

• Forces generated on the foot while a 150 lb man is standing (on 2 legs)? Determine F

• What is tension generated in achilles tendon (connected to gastronemius muscle) during 2 legged stance? Determine T

150

F F

75 lbs

T

R

1.5” 6”

• What is tension generated in achilles tendon (connected to gastronemius muscle) during 2 legged stance? Determine T

• 2 legged stance– 300 lbs of load through gastroc and tendon – Difference between tendons and ligaments?

– Tendon will stretch-by how much? What do we need to calculate strain?

0.8 kg/mm2 would cause 3.5% elongation

Can’t find a modulus and use Hooke’s law-why?

• In fact, σ-ε curve is;– nonlinear – Age– Health– Rate of test– ?? others

• Steel and Aluminum are ‘linear elastic’

• What is force (F) and amount of stretch (ε) if we jump?

Fast

Slow

– flex our knees and push generating a rxn on our feet (F1)and momentum has to change

– Momentum=– Newton said external forces can change

momentum and called it an Impulse

– Need to find velocity

• Jump- raising our potential energy but..conservation of energy we must generate kinetic energy—

• , where g=32 ft/s2 and he jumped 2 ft• So, • F1=• F1=• So, 175# due to impulse and 150# due to weight,

assuming 2 legged jump

• F=

• Go back to FBD,

• Now what is stretch of tendon

150 +175

F F

F

T

R

1.5” 6”

1.8 kg/mm2 would cause 6% elongation

Tendons can fail around 10% strain