Materials Required:
l Nylon rope, or nylon clothesline, 6 to 8 feet long
l Dacron, polyester, or dacron/polyester rope, 6 to 8 feet long
l Water
l 2 big rocks
The help of one of your parents
Procedure:
- Wet both pieces of rope with water from a garden hose or in a sink.
- Ask one of your parents to tie each rope to a tall, sturdy object, such as the cross bar of a swing or a high, solid tree branch.
- Tie a large rock to each of the free ends. Now tug on the ropes by applying downward pressure to the rocks. What do you notice about the properties of the two different kinds of rope? The nylon line increases in length, while the dacron line remains the same.
This Is What Happens:
Sailors and other boaters know about the two different kinds of rope that you tested. Nylon line will stretch a little while it is under tension, so sailors use it to tie their boats to a dock. However, the lines used to fasten the sails to the mast must be as tight as possible so the sails don’t flap needlessly in the wind, and a stretchy rope would not be a good idea. In this case, dacron rope is used.
