Science for fun

I attended the science for fun course with Josiah and Pei Yu. At first i thought that it would be something like a lecture and we had to take notes or something like that. But after I entered the course, i realised it was doing experiments and other interesting stuff. The first experiment that we did was the Hand Boiler. When we squeeze the bulb containing a liquid, the liquid rises to the top of the bulb. Another experiment i like is the Oobleck. It is an example of a non-Newtonian fluid. It can act like a liquid when held loosely in your hand but it can also act like a solid if you apply force on it. When I slowly put my hand into the Oobleck, my hand sinks into it like a liquid. However when we apply force on it, it becomes as hard as a solid. I felt very fascinated with it as I have never encountered anything like that before.

Quicksand is also a non-Newtonian fluid. When undisturbed, it appears to be solid ("gel" form), but when it is disturbed like when a person attempts to walk on it, there is a sudden decrease in its viscosity (a measure of the internal resistance of a fluid). Then the water and sand in the quicksand separate and dense regions of sand sediment form; it is because of the formation of these high volume fraction regions that the viscosity of the quicksand seems to increase suddenly. Someone stepping on it will start to sink. To move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are quite large: to remove a foot from quicksand at a speed of 0.01 m/s would require the same amount of force as "that needed to lift a medium-sized car.”

Because of the higher density of the quicksand, it would be impossible for a human or animal to completely sink in the quicksand, though natural hazards present around the quicksand would lead people to believe that quicksand is dangerous. In actuality the quicksand is harmless on its own, but because it greatly impedes human locomotion, the trapped person is normally harmed by other factors like solar radiation or dehydration.