How Much Elastic Energy Is Stored in the Achilles Tendon?

[dvolpe]

Homework Statement

If the maximum tension in the Achilles tendon when the foot is sent down is 4.5 kN and the tendon's spring constant is 360 kN/M, calculate how much elastic energy is stored in it.

Homework Equations

F = kx
Hookes Law: Energy = 1/2*k*x squared

The Attempt at a Solution

Got x from F = kx x = 0.0125 m this is correct per submission.
Then substituted all values into Hookes law and got energy = .0281 J This was wrong according to submission.

If the elastic energy is a measure of the potential energy, how do I find that?

 

[rock.freak667]

Your formula for energy should work. Did you properly convert the units?

 

[dvolpe]

Yes I converted th distance x of 1.25 cm to .0125 m. The constant is 360 kN/m . Wait..do I need to convert the constant to N/m?
Which then makes the answer -.0281 KJ or -28.1 joules, correct?

 

[rock.freak667]

Yes I converted th distance x of 1.25 cm to .0125 m. The constant is 360 kN/m . Wait..do I need to convert the constant to N/m?
Which then makes the answer -.0281 KJ or -28.1 joules, correct?

Yes. However your answer would be positive and not negative.