Objectives 1: Understand that the pressure is proportional to the surface on which a same force is applied
The following activities will show by experiment the concept of pressure, representing the force applied on a given area. If the same force is applied on a larger area, the pressure decreases.
Another important aspect is that the pressure on a solid depends on the contact area, while for a fluid (i.e. a liquid or a gas), the body is immersed in the fluid so the pressure is applied on all the surface…
The following experiments correspond to the fakir bed experiments, difficult and dangerous to manage in a classroom!
45 minutes
Go to a sand pit and ask the children to flatten the sand.
Then you tell them that you are going to put your feet in the sand with the stilt, the normal shoe and the snowshoeing.
What do your students expect to see?
Ask what is the difference for them?
You can also show them the fakir and ask them why he seems so comfortable on his nail bed?
Step 1 :3 nails
Step 2 : 20 nails
The way this experiment is proposed here is just to understand the principle of pressure with solid. You can always apply a more scientific approach by varying parameters such us number of nails, thickness of the play dough, changing the position of the glass of water, …
When applying a given force on a solid surface, the resulting pressure will be function of the surface.
If the surface increases, the pressure decreases, and if the surface decreases the pressure increases.
Again quantification of this law will be made with students above 11 years old.