Walking on water
surface area
So what is this
surface area
(check out this definition on the online science dictionary) thing that can make chunks of metal, like ships float?
Have you ever tried to float in water while “upright” - in other words, trying to stand in water. If you don't move your arms and legs, guess what, you're going down!
But try and float on your back, with your arms stretched out. Much easier, hey?! It is because there is more of you on top of the water.
Still not quite following? Let's do the project and the experiment and then you will see exactly what is happening...
Let's do science ...
The project – step by step
The Question
How can heavy objects, that normally sink, float in water?
The Hypothesis
When the surface area of an object is big enough it will float because there is more water holding it up.
The Experiments
My plasticine can float!
Why this experiment?
This experiment will show that by taking something, i.e. plasticine, which normally sinks, and increasing the area that is in touch with the water, it can be made to float. This directly proves the hypothesis.
The Conclusion
By making the surface area of an object big enough, you can get it to float because there is more water holding it up.
“Beef up your project” facts
A lot of mankind's amazing discoveries and inventions were being used long before we made use of them, in nature. Just one example of where a large area in the right place on the animal's body, lets the animal move easier:
The good old camel. If you have ever tried to run on the beach, you will know how difficult and tiring it can be. Camels walk (and sometimes run) on sand most of their lives. They have extra large hooves, which helps them to walk on top of the sand. In fact, with their over-sized clod-hoppers, it is unlikely that you will find sneakers to fit a camel!
More...
Small surface areas also have their place. An example, pins work really well because their tip is sharp, i.e. there is a really small area at the end of the pin. Here is something to try:
Take your piece of plasticine that you used for the experiment and roll it into a ball about 1,5 cm in diameter. Take a pin and push it into the plasticine – easy – not much effort required. It is easy to push all the way through.Now take a pencil and do the same. Not so easy to get it through.Now try it again with the back of the pencil. Hmmm! The larger the surface area the more effort needed to push the object through the plasticine – BUT – the smaller the surface area, the easier it is to push the object into the plasticine!
Hey, just thinking about it, you could use this as part of your display, just to score a couple of more points with the judges.
Here is a story that goes with this bit (you could add this to your “Beef up your project” facts):
In the “old days” when most shops still had wooden floors, stilleto heeled shoes became a very popular fashion item among ladies. Stilleto heels are very tall and very thin heels.
The small bit of the heel that made contact with the ground carried the whole weight of the lady. The small surface area meant that they almost acted as pins on the wooden shop floors. This left the shop floors with dozens of stilleto heel holes all over them!
Some shops owners even ended up baning the wearing of stilleto heels in their shops! Give me sneakers any day!
|
