Forces and Pressure in Fluids Forces in Fluids Chapter 13 Section 2 Physical Science

Pressure in Fluids In the last section, we learned a fluid exerts pressure equally in ALL directions at a given depth This means that at the same depth the pressure is equal in all directions The lower you go the more pressure This is why a larger stream of water came out the bottom hole of the 2 liter

Pascal’s Principal Pascal’s Principal: The forces on the walls in bottle A is equal at any given depth Pascal’s Principal: A change in pressure at any point in a fluid is transmitted equally in all directions When squeezed, the pressure is transferred equally, not just where you squeeze

Hydraulic Systems A hydraulic system uses pressurizes fluid acting on pistons of different sizes to change a force Applies Pascal’s Principal

Bernoulli’s Principal Swiss scientist Daniel Bernoulli discovered the reason why a sheet of paper rises when you hold the corners and blow over the top surface Bernoulli’s Principal says that as the speed of a fluid increases, the pressure within the fluid decreases From yesterday, the top of the paper has a decrease in pressure while the bottom of the paper has an increase in pressure causing the paper to rise

Bernoulli’s Principal This also explains the ping pong ball on the hair dryer. The stream of air causes the ball to rise. The pressure in the air stream is lower than the surrounding air. If the ball moves out of the stream, it encounters high pressure and that forces the ball back into the low pressure air stream.

Bernoulli’s Principal This also explains the devastating effects of a hurricane The wind blows over the roof, creating low pressure. The difference in pressure of the house structure results in a strong upward force that can lift the roof off the house

Bernoulli’s Principal This also explains the ability of birds and airplanes being able to fly The air moves over the top of the wing faster than the bottom creating lower pressure on top The high pressure under the wing causes it to rise This upward force is known as lift

Bernoulli’s Principal Wings can also create a downward force This can be seen in a spoiler. It pushes the tires onto the road and gives the car better traction. Now you can take the corners at higher speeds

Bernoulli’s Principal This concept can also be applied to spray bottles The fast moving water from the hose creates low pressure. The pressure difference forces the solution up the tube. The solution mixes with the water and sprays out of the container