Hemp is one of the strongest fibres with a very high tensile strength and is extremely rigid. Hemp ropes were the first to be used for ship rigging which adjusted the position of the sails and supported the masts.
However, rock climbers use nylon ropes to break their fall as they can stretch considerably under tension.
A climbing equipment company tests their ropes by attaching an 80 kg mass to an end of the rope and releasing it from a ledge.
Fig. 1.2 shows the results of a test carried out to compare the time it takes for a nylon rope and a hemp rope to return to their unstretched length after beginning to stretch.
Fig. 1.2
Rope |
Time to return to unstretched length / s |
Nylon |
0.664 |
Hemp |
0.035 |
In the test, both ropes used had identical unstretched lengths of 19.0 m and diameters of 10 mm.
Show that the average resultant force exerted by the hemp rope is about 20 times larger than the average resultant force exerted by the nylon rope.