Answer
(a) The spring constant of the tendon is $3.2\times 10^5~N/m$
(b) The muscle did $20~J$ of work stretching the tendon.
Work Step by Step
(a) We can find the spring constant of the tendon:
$k = \frac{\Delta F}{\Delta x} = \frac{4800~N-3200~N}{0.0050~m} = 3.2\times 10^5~N/m$
The spring constant of the tendon is $3.2\times 10^5~N/m$
(b) We can find the average force required to stretch the tendon:
$F_{ave} = \frac{4800~N+3200~N}{2} = 4000~N$
We can find the work required to stretch the tendon:
$Work = F_{ave}~d = (4000~N)(0.0050~m) = 20~J$
The muscle did $20~J$ of work stretching the tendon.
