If you live in Hong Kong, and if you cross the harbour on the lower deck of a Star-Ferry boat, you will notice that the sailor can halt the boat with rope as in Fig. 1 below :

(Note that we derive the differential equation using infinitesimal, this is a very common way to get a differential equation. There is another way, by theoretical derivation. Infinitesimal and theory are 2 main methods to get differential equations. There is a danger in using infinitesimal, because we may miss out something in the diagram, which is so subtle that we cannot realize it, e.g. in some mechanic problem, if we use Lagrange Equation to get the differential equation, and also use infinitesimal to get the differential equation, very often, we find the 2 equations differ, and the difference is so small, that the solutions do not differ much. But still, infinitesimal is a very useful way to get the equation and understand the phenomena, and in majority of cases, give correct equation.)

Boy scouts and sailors learn rope work. There are many types of knots. One thing to remember is that if you wind the rope many times, the knot is sure to be tight.

Bamboo scaffolding

In ancient times, when modern materials were unavailable, Chinese people use bamboo for all sorts of construction : scaffolding, huts. Even large buildings may be constructed out of bamboo. Its theory is the same as above, and the practical construction is shown below:

Originally, the rope to wind around is also made from bamboo : peeling very thin slices, using a sharp knife, from bamboo. Nowadays, people in Hong Kong use synthetic rope, which is made very strong in the longitudinal direction.

In the wild, we may use tree branches instead of bamboo, and vine instead of rope. Climbing vine are very common in the wild, and most of them are very strong longitudinally.

If you live in a city, you may find some pieces of tree branches, or even used broom-stick, and COPPER WIRE, those electric wires used in home (there are 2 wires inside, colored red and black, usually. There is no need to take away the insulation). And practice making miniature huts, platforms, shelters, etc.

If you live in Hong Kong, or happen to pass by or travel here, have a look at the bamboo scaffolding, and see the workers' handiwork.

[Back to Home Page]