How Much Energy is Absorbed Elastically When a Person Lands on Their Feet?

[debzrie]

Homework Statement

A 60 kg person lands on their 2 feet on a floor with a speed of 3.5 m/s.?
Energy dispatched in a variety of ways, including compression in the cartilage of your knees, in the soles of your shoes etc. calf and thigh muscles have a major role. elastic stretching of your Achilles tendon also plays a part.
a) if the extension of the tendon is 0.010m and is the maximum force (in one tendon) is 1800 N, how much energy is absorbed elastically? state any key assumption made.
b) what fraction of the energy just prior to impact is absorbed in this way?

Homework Equations

I'm so confused I have no idea :(

The Attempt at a Solution

 

[Andrew Mason]

Homework Statement

A 60 kg person lands on their 2 feet on a floor with a speed of 3.5 m/s.?
Energy dispatched in a variety of ways, including compression in the cartilage of your knees, in the soles of your shoes etc. calf and thigh muscles have a major role. elastic stretching of your Achilles tendon also plays a part.
a) if the extension of the tendon is 0.010m and is the maximum force (in one tendon) is 1800 N, how much energy is absorbed elastically? state any key assumption made.
b) what fraction of the energy just prior to impact is absorbed in this way?

Think of the tendon as a spring that is stretched from 0 to .01 m in stopping the fall. What is the spring constant k of that spring? How much energy is stored in that spring when stretched to .01 m? How much energy does the person have just before landing? How much of that energy can be stored in those tendon springs?

AM

 

[debzrie]

still a little confused :S

 

[Andrew Mason]

still a little confused :S

What are you confused about?

Can you determine the energy of the person just before landing? Can you determine the spring constant of the tendons?

AM