An estimated 3kg-Gromit was tied to a bungee cord to clean the windows of Wendolene Ramsbottom's wool shop. The other end of the bungee cord was tied 7m above the ground. The bungee measures 4.5m in its relaxed state and we can assume that it obeys Hooke's Law with a spring constant of k=100N/m. We assume that Gromit jumped from the point of suspension of the bungee.
a) If gromit stops before he reaches the ground, what is the height h of his waist above the ground at his lowest point?
b) What is the net force on him at the height (h+d) above the ground at his lowest point?