Answer to Question #294537 in Mechanical Engineering for yokhyuni

Question

Design a project to determine the specifications (unstretched length) spring constant k as 100N/m for the elastic cord to be used at a bungee-jumping facility. Participants are to jump from a platform 45m above the ground. When they rebound, they must avoid an obstacle that extends 5 m below the point at which they jump. In determining the specifications for the cord, establish reasonable the safety limits for the minimum distances by which participants must avoid the ground and obstacle. Account for the fact that participants will have different weight. (Specify a maximum allowable weight for participants of 100kg, and Maximum height of 1.7m)

Answer 1

Natural rubber is widely used for cords used in bungee jumping. The fabric covering for the bungee cord may be braided from cotton or nylon yarn. Commercial bungee cord usually has a single layer of nylon covering which is more resistant to abrasion and has a higher tensile strength.

Bungee Cord Specifications

Practical Uses

Manufacturers make bungee cord from usually either natural or synthetic rubber. Natural rubber, also called latex rubber, can be extended in its shape and has high resilience. It also regains its original shape well after being stretched, called tensile strength. Standard bungee cords come in diameters ranging from 1/4 inch to over 3/5 inch. 

recreational Uses

Bungee cords used for bungee jumping come in two basic designs. Some jumpers prefer mil-spec cords, the original design used for most everyday-use bungee cords.

Manufacturing Bungee Cords

Manufacturing bungee cords begins with preparing and extruding long ribbons of natural or synthetic rubber. The ribbons measure .09 to .12 inches thick, .25 inch wide and up to 100 feet long. When the rubber ribbons cool they are coiled together and shipped to a bungee cord manufacturer.

 Bungee Safety 

When stretching the cords for holding items in place, energy builds up and can suddenly be released if an end is let go or not attached well. Bungee cords travel up to 60 mph when released, and cause injuries each year, especially to the eye.