This experiment is based on Archimedes principle of buoyancy, it is not clearly uses this principle as forces are affected by other things also. It works in partially closed system and shows exact result. In simple way just fill pouch with water so when some force applied over tube then water come out of tube will be equal to magnitude of force.
Archimedes' principle indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces. Archimedes' principleis a law of physics fundamental to fluid mechanics. For more info please visit
If you see my previous instructables, you will find a project named "Archimedes weigh scale". this project is very similar to it but made with different material which are easily available.
I also made a small video of making if you are video learner please go through it..
Step 1: Material Required
For this instructable we are using very common and easily available material.
1 empty pouch, you can use any pouch with minimum capacity of 200 grams.
1 transparent straw
04 any bolts/studs/anchor fastener with 75 mm length
needle file to make holes
hot glue gun
Step 2: Make Water Reservoir
In this instructable we are using a empty pouch as water reservoir.
Insert straw in pouch and glue it with hot glue. Seal mouth of pouch with hot glue. Excess glue will avoid leak from mouth.
You can check my old instructable for full scale project.
Step 3: Make Frame for Pouch
I made a frame with 02 cardboard sheet.
Drill 04 holes in corner of top sheet and also cut a slot to accommodate straw.
Now take measurement of holes and mark it on bottom plate.
Glue 04 sliding pin on mark. These sliding pin will keep top plate in balance position. And will help to give correct reading.
Glue a small rectangular piece over bottom plate. Also paste a white paper over it. This is for marking readings.
Step 4: Assembly and Water Filling
Fill pouch with water and remove all air from pouch. As air is compressible so if there is air residue then it can affect performance of weigh scale. So be careful while filling.
In end of filling add some food coloring to water. This will be helpful to identify water level easily.
To assemble weigh scale, keep bottom plate then pouch and then top plate. Basically we are sandwiching pouch in between two cardboard plates.
Now stick straw to marking plate with help of double sided tape.
Step 5: Calibration
Calibration is most important part as total performance is depend on it.
I didn’t had small weights so I used water as calibration medium.
As we know
Weight of 1 liter water = 1 kg i.e 1000 ml = 1000 grams.
Take a syringe for calibration. Keep a weightless container over weigh scale.
First mark base line or zero line to current level.
Keep adding some water till water level moves. In my case threshold value was 35 grams i.e water level change its position after 35 ml(35 grams) added to container.
Now keep adding water and mark water level as per your requirement.
Step 6: Testing and “the Eureka” Experiment
Initial reading was not correct as there is some air residue in pouch but after removing air all reading were very correct. I measured different weight and then moved to experiment.
For this experiment I used 175 ml container and a soap (75 grams weight)
So this experiment was to check Archimedes principle which states that a body partially or completely immersed in a fluid is buoyed by force equal to the weight of the fluid displaced by body.
So if I fill container full of water and immerse weighted thing in it then water displaced i.e overflow water weight will be equal to immersed body.
So I fill water in container and measure it which is around 175 grams. Then I keep container is dish and immerse a soap in it, then collected water in another container and measured it. It was perfectly 75 grams i.e weight of soap.
Hence proved. This is very unique way to explain Archimedes principle to students.
Thanks for reading and happy making.