Force and equilibrium: Testing new suture material

Researchers are interested in developing a new type of suture for in-combat medical emergencies. They are tasked with developing a strong, flexible, and versatile thread for this purpose. The lead researcher suggests using a hybrid string composed of various materials. This idea is based on the strength of spider webs, which contain many different types of silk. The combined qualities of the silks allow for extraordinary amounts of flexibility and strength in the webs. The researcher proposes that the same might hold true for combat sutures.

The research team develops a thread that combines polyester, silk, and nylon. They then test this polyfilament by developing an apparatus to determine its strength. A box of mass $4.0\text{kg}$‍ hangs from rest from two of these strings as seen in Figure 1. String A is horizontal and connected to the wall. String B is connected to the ceiling at an angle of $30$‍ degrees. For all of the following questions, assume that $\text{g}=10{\text{m/s}}^2$‍.

Figure 1. The testing apparatus for the strings.