The Achilles tendon will stretch and then rebound, storing andreturning energy during a step. We can model this motion as that ofa mass on a spring. This is far from a perfect model, but it doesgive some insight. If a 60kg person stands on a low wall with herfull weight on the ball of one foot and the heel free to move, thestretch of the Achilles tendon will cause her center of gravity tolower by about 2.5mm.
A. What is the spring constant of her Achilles tendon?
B. If she bounces a little, what is her oscillation period?
C. When walking or running, the tendon spring begins to stretch asthe ball of the foot takes the weight of a stride, transformingkinetic energy into elastic potential energy. Ideally, the cycle ofthe motion will have advanced so that potential energy has justfinished being converted back to kinetic energy as the foot leavesthe ground. What fraction of an oscillation period should the timebetween landing and liftoff correspond to? Given the period youcalculated above, what is this time?
D. Sprinters running a short race keep their foot in contact withthe ground for about .10sec, some of which corresponds to the heelstrike and subsequent rolling forward of the foot. Given this, doesthe answer to part c make sense?
The Achilles tendon will stretch and then rebound, storing andreturning energy during a step. We can model this motion as that ofa mass on a spring. This is far from a perfect model, but it doesgive some insight. If a 60kg person stands on a low wall with herfull weight on the ball of one foot and the heel free to move, thestretch of the Achilles tendon will cause her center of gravity tolower by about 2.5mm.
A. What is the spring constant of her Achilles tendon?
B. If she bounces a little, what is her oscillation period?
C. When walking or running, the tendon spring begins to stretch asthe ball of the foot takes the weight of a stride, transformingkinetic energy into elastic potential energy. Ideally, the cycle ofthe motion will have advanced so that potential energy has justfinished being converted back to kinetic energy as the foot leavesthe ground. What fraction of an oscillation period should the timebetween landing and liftoff correspond to? Given the period youcalculated above, what is this time?
D. Sprinters running a short race keep their foot in contact withthe ground for about .10sec, some of which corresponds to the heelstrike and subsequent rolling forward of the foot. Given this, doesthe answer to part c make sense?
