f t r f t r 1.5” 6” forces generated on the foot while a 150 lb man is standing (on 2 legs)?...
Post on 19-Dec-2015
212 views
TRANSCRIPT
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