Chapter 3: States of Matter Section 3: Fluids

BELLRINGER Take out a sheet of paper, tear it in half and share with a neighbor. You will have 5 minutes to complete these 4 questions. If the concept is unfamiliar to you, take an educated guess.

Bellringer 1. 2. 3. 4. 1. Is the buoyant force on the lump of gold greater than, less than, or equal to the gold’s weight? 2. Is the buoyant force on the balloon greater than, less than, or equal to the balloon’s weight? 3. Is the buoyant force on the boat greater than, less than, or equal to the boat’s weight? 4. Is the buoyant force on the submarine greater than, less than, or equal to the submarine’s weight?

Pressure is the amount of force exerted on a given area of surface. Section 3: Fluids You’ve probably heard of air pressure, blood pressure, and water pressure…but, what is pressure? Pressure is the amount of force exerted on a given area of surface.

Which of the following states of matter can flow? Solids Liquids Gases Plasmas Both Liquids and Gases Both Solids and Plasmas 30

REMEMBER BECAUSE THE PARTICLES OF LIQUIDS AND GASES SLIDE PAST ONE ANOTHER, THEY ARE SAID TO FLOW.

Pressure How do fluids exert pressure? Fluids exert pressure evenly in all directions. pressure: the amount of force exerted per unit area of a surface example: when you pump up a bicycle tire, air particles constantly push against each other and against the tire walls

PRESSURE Pressure is calculated by dividing force by the area over which the force is exerted.

The SI Unit for measuring pressure is called the PASCAL. One pascal (1 Pa) is the force of one newton exerted over the area of one square meter (1 N/m2). Newtons are the SI Unit used to measure force.

Buoyant Force The upward force that keeps an object immersed in or floating on a fluid. If you push a rubber duck to the bottom of the tub, what happens when you let it go?

What unit do we use to measure pressure? Pascal Newton Meter Gram 30

What unit do we use to measure length? Pascal Newton Meter Gram 30

What SI unit do we use to measure force? Pascal Newton Meter Gram 30

Buoyant Force

Buoyant Force, continued Archimedes’ principle is used to find buoyant force. The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces.

Comparing Weight and Buoyant Force

Buoyant Force, continued An object will float or sink based on its density. If an object is less dense than the fluid in which it is placed, it will float. If an object is more dense than the fluid in which it is placed, it will sink.

Bellringer 1. 2. 3. 4. 1. Is the buoyant force on the lump of gold greater than, less than, or equal to the gold’s weight? 2. Is the buoyant force on the balloon greater than, less than, or equal to the balloon’s weight? 3. Is the buoyant force on the boat greater than, less than, or equal to the boat’s weight? 4. Is the buoyant force on the submarine greater than, less than, or equal to the submarine’s weight? LESS THAN GREATER THAN EQUAL TO EQUAL TO

MEMORIZE ARCHIMEDES’ PRINCIPLE (write it 5 times). FOR HOMEWORK MEMORIZE ARCHIMEDES’ PRINCIPLE (write it 5 times). The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces. Questions 1 & 2 on page 94.

BELLRINGER TODAY, YOU WILL ONLY HAVE 90 SECONDS TO ANSWER THE BELLRINGER QUESTION.

BELLRINGER #1 State Archimedes’ Principle.

BELLRINGER #2 1. How does the ship’s density compare with the density of the water?

Pascal’s Principle When you squeeze on one of an unopened tube of toothpaste, what happens? The reason the toothpaste comes out the other side is because we applied pressure to one end of the tube and that pressure is transmitted throughout the tube.

Pascal’s Principle What happens when pressure in a fluid changes? Pascal’s principle states that a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid. In other words, if the pressure in a container is increased at any point, the pressure increases at all points by the same amount. Mathematically, Pascal’s principle is stated as P1 = P2. Because P = F/A, Pascal’s principle can also be expressed as F1/A1 = F2/A2.

Pascal’s Principle, continued Hydraulic devices are based on Pascal’s principle. Because the pressure is the same on both sides of the enclosed fluid, a small force on the smaller area (left) produces a much larger force on the larger area (right). The plunger travels through a larger distance on the side that has the smaller area.

Math Skills Pascal’s Principle A hydraulic lift uses Pascal’s principle to lift a 19,000 N car. If the area of the small piston (A1) equals 10.5 cm2 and the area of the large piston (A2) equals 400 cm2, what force needs to be exerted on the small piston to lift the car? 1. List the given and unknown values. Given: F2 = 19,000 N A1 = 10.5 cm2 A2 = 400 cm2 Unknown: F1

Math Skills, continued 2. Start with Pascal’s principle, and substitute the equation for pressure. Then, rearrange the equation to isolate the unknown value. P1 = P2

Math Skills, continued 3. Insert the known values into the equation, and solve. F1 = 500 N

Fluids in Motion What affects the speed of a fluid in motion? Fluids move faster through small areas than through larger areas, if the overall flow rate remains constant. Fluids also vary in the rate at which they flow.

Fluids in Motion, continued Viscosity depends on particle attraction. viscosity: the resistance of a gas or liquid to flow Fluid pressure decreases as speed increases. This is known as Bernoulli’s principle.

Viscosity

For homework, complete the Concept Review for Section 3. There will be a reading quiz tomorrow.