Make a pen cap sinker to demonstrate Pascal’s law
Pascal’s law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. This means that if you apply pressure to a small area of a fluid, the pressure will be transmitted throughout the entire fluid equally. This is why hydraulic systems work so well, as the pressure applied to one end of the system will be transmitted to the other end, allowing for the transfer of force or energy.
Pascal’s law has many practical applications, including hydraulic lifts, brakes, and jacks. It is also used in many industrial and manufacturing processes, such as in the production of plastics, metals, and chemicals. Here we will demonstrate Pascal’s law with a pen cap and plastic bottle.
- Fill the plastic bottle with water.
- Attach a piece of clay to the arm of a plastic pen cap.
- Put the cap in the bottle so that it floats.
- Put the lid on the bottle and tighten so that it does not leak any air.
- Squeeze the sides of the bottle.
What do you think causes the pen cap to sink when you squeeze the sides of the bottle? By squeezing the bottle, you increase the pressure inside, thus forcing more water up into the pen cap. The added water in the cap increases its weight and causes the cap to sink.
Submarines operate on the same principle
A submarine works along these same principles. If the average density of the submarine is less than that of the water, then the submarine will float. If the average density of the submarine is more than that of the water, then the sub will sink (or dive in submarine terminology). While the submarine contains a lot of air (which would make it float since the density is less than that of the water) it also contains a lot of steel (which has a high density). So you see, it’s the average density that makes the submarine act the way it does. How can you change the average density of the sub ‘on the fly’ to make it float or sink on command? Just like with the pen cap, water is pumped in and out of ballast tanks by the submarine crew.
If a fluid is at rest, pressure is transmitted equally to all its parts and, at any one point, is the same in all directions. The fluid acts this way because the molecules in it move freely. The molecules are far apart in a gas and comparatively close together in a liquid.
The French scientist Blaise Pascal discovered the fact that pressure in a fluid is transmitted equally to all distances and in all directions. He formulated Pascal’s law to describe the effects of pressure within a liquid. Blaise Pascal was a polymath who made significant contributions to many fields of study, and is widely regarded as one of the most important thinkers of the 17th century.
Interesting note about Blaise Pascal
Despite his many achievements, Pascal was also known for his introspective and spiritual writings, which are considered some of the most influential works in French literature. He had a profound religious experience in 1654, which led him to devote the rest of his life to the study and practice of Christianity.
Required supplies for the homemade pen cap sinker experiment
Supplies: Plastic bottle, Pen cap, Clay
In-Article Image CreditsFour blue, red, black and green BIC pens and four pen caps via Wikimedia Commons by Carlos Delgado with usage type - Creative Commons License. June 3, 2012
Featured Image CreditFour blue, red, black and green BIC pens and four pen caps via Wikimedia Commons by Carlos Delgado with usage type - Creative Commons License. June 3, 2012