Question
Suppose we replace the 4.0-kg book in Exercise 9.31 of the biceps muscle with an elastic exercise rope that obeys Hooke’s Law. Assume its force constant $k = 600 \textrm{ N/m}$. (a) How much is the rope stretched (past equilibrium) to provide the same force $F_B$ as in this example? Assume the rope is held in the hand at the same location as the book. (b) What force is on the biceps muscle if the exercise rope is pulled straight up so that the forearm makes an angle of $25^\circ$ with the horizontal? Assume the biceps muscle is still perpendicular to the forearm.
1. $0.79 \textrm{ m}$
2. $4.1\times 10^{3}\textrm{ N}$