Which materials are composed of proteins, providing high tensile strength?

Muscles are materials that are composed of many flexible and contracting cells and tissues that helps the human body to move, generate involuntary or voluntary movement or motion. 

These are composed of many high tensile strength that is developed by the cells that generate important proteins for the muscle to work and process. 

If the experiment was perfomed more then once and you get the same results

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.