You are holding a thin and weightless bar on your head (see figure 2.1). On the extremity 4, the bar is attached to an elastic spring with unstressed length of 1 m and spring constant, k = 50 N/m; on the other extremity D, the bar is against a wall. On point C, a force F is applied, forming a 45-degree angle with the bar. Assign the length AE according to the height of your body. (a) What is the magnitude of the force F for the bar to rest horizontally? (b) If the force F was removed, what support would you need in D in place of the wall, in order to keep the bar at rest horizontally? Justify your suggestion(s). State and justify your assumptions and comment on your solutions. 2m Im Im 4m Figure 2.1 D

You are holding a thin and weightless bar on your head (see figure 2.1). On the extremity 4, the bar is attached to an elastic spring with unstressed length of 1 m and spring constant, k = 50 N/m; on the other extremity D, the bar is against a wall. On point C, a force F is applied, forming a 45-degree angle with the bar. Assign the length AE according to the height of your body. (a) What is the magnitude of the force F for the bar to rest horizontally? (b) If the force F was removed, what support would you need in D in place of the wall, in order to keep the bar at rest horizontally? Justify your suggestion(s). State and justify your assumptions and comment on your solutions. 2m Im Im 4m Figure 2.1 D