Physics 10 grade Paskal's law

Communicating vessels. Application of Pascal’s law. Torricelli's experiment. Atmospheric pressure.

Learning objectives

10.1.3.2 – to describe the Pascal’s law and its application;

10.1.3.3 – to explain the term of hydrostatic pressure;
 

Pascal's law (also Pascal's principle or the principle of transmission of fluid-pressure) is a principle in fluid mechanics that states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.

Pressure in the liquids

Explain the results of the experiment

Hydrostatic paradox

The proposition in hydrostatics that any quantity of water, however small, may be made to counterbalance any weight, however great; or the law of the equality of pressure of fluids in all directions

p = ρ h g

Torricelli's experiment

https://www.youtube.com/watch?v=drI0d6An84g

At constant atmospheric pressure the water column height is 10.3 m. How can you calculate the height of the remaining fluid in the remaining two tube?

Pressure intensity produced by the force F, p = F/Area of plunger = F/a

As per Pascal’s law, the above intensity p will be equally transmitted in all directions.

Therefore, The pressure intensity on ram = p = F/a = W/A or W= F(A/a)

Above Equation indicates that by applying a small force F on the plunger, a large force W may be developed by the ram..

https://www.youtube.com/watch?v=VxLTDtaRCZk

Hydraulic Jack

When a hydraulic pump operates, it creates a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line to the pump and by mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.

Hydraulic pump

Test your knowledge

1) Put the glass Cup into water, turn it under water and fill with water, slowly lift. Why won't the water spill until the edge of the glass comes out of the water?

2) fill the glass with water, cover its surface with one sheet of paper. Hold the sheet by hand and quickly flip the Cup. Now explain that when you receive the hand, the water will not spill.

3) Why can't the atmospheric pressure be considered as the water column pressure?

In 1648 Blaise Pascal made the following experiment. He installed a very thin long tube in a wooden barrel, then went up to the second floor of the house and poured one glass of water into the tube. Since the tube is narrow, the water level was very high. The iron jars of the barrel could not withstand much pressure, the barrel exploded. Can you explain why?

Pascal's experiment

"Magdeburg hemispheres".

In 1654 Otto von Guericke experimented with the famous "Magdeburg hemispheres". To view the experiment was attended by members of the Emperor Ferdinand III and the Regensburg Reichstag. They were witnesses to the fact that the two hemispheres, aspirated air, not handed out a few double names. Can you explain why?

The hemispheres of Magdeburg are present in the body of every person: in the hip joint of the head of bones are supported by atmospheric pressure.

Effect of atmospheric pressure

How we breathe? The respiratory mechanism is as follows: muscle strength we increase the volume of the chest, the air pressure in the heel is reduced, and atmospheric pressure pushes part of the air to the chest. At the exit, on the contrary.

Effect of atmospheric pressure

Effect of atmospheric pressure

How we drink? Put a glass on your lips, we take the liquid ourselves. Scheme of liquid dilutes the expansion of the chest, the air of the lungs and oral cavity, and atmospheric pressure at the place of "attracts"another part of the liquid. Therefore, the human body adapts to atmospheric pressure and uses it.

There are many living organisms such as worms, octopuses, leeches and pumps that stick to any shape

Effect of atmospheric pressure

Pumps for domestic use are made of an elastic substance. Under the influence of hand pressure, the air under the pump is withdrawn outwards, after which the elastic substance is restored, the air pressure under the air is less than the external atmospheric pressure.