13.2 Forces and Pressure in Fluids

13.2 Forces and Pressure in Fluids

MONDAY, MARCH 28, 2011 - REG section 3.2 fluidsOPENER #1 - Periods 3, 4, & 6

1. How can you predict if an object will float in a liquid? 2. Is it possible for liquids to float on liquids? Give an example or counter example.3. What does the word viscosity mean? (prior knowledge & chapter)

CW: Notes “PAP 13.1-13.2 or REG 3.2” - Fluids, pressure, Bernoulli’s Principle, etc.QUIZ next Wednesday on the small unit of study...Your group has until April 8th to have converted your iMovie into a movie and dropped in my IN BOX to not lose any points. You will need to work on this at lunch, before school, or after school in the next couple of weeks.

HW REG: pg. 84 #1 AND pg. 86 #1-9 due TOMORROW. This is the first grade of the 9 weeks. Start out with 100%! (3 incomplete assignments will be write up in my class this 9 weeks. 1 day late may count up to 1/2 credit only in my class; other teachers may not give any.)

FIELD TRIP WEDNESDAY - Others will report to Coach Bock Room in Bldg. 18.

13.2 Forces and Pressure in Fluids

MONDAY, MARCH 28, 2011 - PAP ch. 13 OPENER #1 PAP - periods 5, & 7 - 5th period has an assembly FIRST

1. How can you predict if an object will float in a liquid? 2. Is it possible for liquids to float on liquids? Give an example or counter example.3. What does the word viscosity mean? (prior knowledge & chapter)

CW: Notes “PAP 13.1-13.2 or REG 3.2” - Fluids, pressure, Bernoulli’s Principle, etc.QUIZ next Wednesday on the small unit of study...Your group has until April 8th to have converted your iMovie into a movie and dropped in my IN BOX to not lose any points. You will need to work on this at lunch, before school, or after school in the next couple of weeks.

HW REG: pg. 84 #1 AND pg. 86 #1-9 due TOMORROW. This is the first grade of the 9 weeks. Start out with 100%! (3 incomplete assignments will be write up in my class this 9 weeks. 1 day late may count up to 1/2 credit only in my class; other teachers may not give any.)

FIELD TRIP WEDNESDAY - Others will report to Coach Bock Room in Bldg. 18.HW PAP: pg. 393 #1-9 due Tuesday AND pg. 397 #1-8 DUE FRIDAY.

13.1 Fluid Pressure

Because the theater seat exerts a supporting force over a larger area, it is more comfortable than the bicycle seat.

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How is pressure calculated?

To calculate pressure, divide the force by the area over which the force acts.

Pressure

13.1 Fluid Pressure

Pressure is the result of a force distributed over an area. examples nail, sharp pencil, snow shoes

• The unit of force is the newton (N).• The unit of area is the square meter (m2). • The SI unit of pressure is the pascal (Pa). A pascal is

one newton per square meter (N/m2)• 1 kPa = 1000 Pa

Pressure

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If the area of a box touching the ground is 1.5 square meters, and its weight is 2700 newtons, what pressure does the box exert on the ground?

Pressure

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A fluid is a substance that assumes the shape of its container.

• Both liquids and gases are fluids. • Water, oil, gasoline, air, and helium are examples

of fluids.

Pressure in Fluids

Fluids: Anything

that Flows: Liquids, Gases, Plasma

The direction of flow is always FROM high pressureTO low pressure.

Low pressure

High pressure

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How does water pressure change with depth?

How is pressure distributed at a given level in a fluid?

Pressure in Fluids

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Water pressure increases as depth increases. The pressure in a fluid at any given depth is constant, and it is exerted equally in all directions.

Pressure in Fluids

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A. Particles in a liquid are tightly packed together but are able to slide past one another.

Pressure in Fluids

13.1 Fluid Pressure

B. Particles in a gas are far apart and travel in straight lines until they collide with another particle or object.

Pressure in Fluids

13.1 Fluid Pressure

Water in a glass is in contact with the walls and bottom of the glass, and it exerts pressure on these surfaces.

For a fluid that is not moving, depth and the type of fluid are the two factors that determine the pressure the fluid exerts.

Pressure in Fluids

13.1 Fluid Pressure

Each vase holds a different amount of liquid. The liquid levels are all the same because pressure depends on depth, not amount.

Pressure in Fluids

13.1 Fluid Pressure

The layer of gases surrounding a planet is known as its atmosphere. All of the planets in our solar system have some form of atmosphere. The weight of an atmosphere creates atmospheric pressure at the planet’s surface.

The weight of the Earth’s atmosphere exerts a pressure of about 101 kPa (1 atm) at sea level.

Planetary Atmospheres

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Exploring Boiling Points of Chlorocarbons

1. Interpreting Tables Which planet listed in the table has the greatest atmospheric pressure?

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1. Interpreting Tables Which planet listed in the table has the greatest atmospheric pressure?

Answer: Venus, 9120 kPa

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2. Interpreting Tables What chemical substance exists in all but one of the atmospheres?

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2. Interpreting Tables What chemical substance exists in all but one of the atmospheres?

Answer: Nitrogen

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3. Converting Units The bar is another unit of pressure (1 bar = 101.3 kPa). Convert each of the given pressures into bars.

13.1 Fluid Pressure


3. Converting Units The bar is another unit of pressure (1 bar = 101.3 kPa). Convert each of the given pressures into bars.

Answer: Mercury, 10–15 bar; Earth, 1 bar; Venus, 90.0 bar; Mars, 0.0070 bar

13.1 Fluid Pressure


4. Using Formulas How much force is exerted on a 2.00-square-meter area of Venus’s surface?

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4. Using Formulas How much force is exerted on a 2.00-square-meter area of Venus’s surface?

Answer: Pressure = Force/Area; Force = Pressure × Area;

Force = 9120 kPa × 2.00 m2 = 9.12 × 106 N/m2 × 2.00 m2 Force= 18240000 = 1.824 x 107 or rounded to sig. figure 2.00 × 107 N

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3. Predicting On which planet would a balloon filled with a given quantity of helium have the smallest volume?

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3. Predicting On which planet would a balloon filled with a given quantity of helium have the smallest volume?

Answer: The helium-filled balloon would have the smallest volume on Venus because Venus has the greatest atmospheric pressure.

13.1 Fluid Pressure

How does air pressure change with altitude? Air pressure decreases as the altitude increases.

Air Pressure and the Atmosphere

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Earth’s atmosphere exerts pressure of about 101 kPa at sea level. Why aren't you crushed by air pressure?


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Earth’s atmosphere exerts pressure of about 101 kPa at sea level. Why aren't you crushed by air pressure?

The pressure inside your body balances the air pressure outside. The balanced forces cancel, resulting in a net force of zero.


13.1 Fluid Pressure

Why do your ears pop when you change altitude such as climbing a large mountain in a car or rising in an airplane? Why don’t your ear drums burst on the airplane?

13.1 Fluid Pressure

Why do your ears pop when you change altitude such as climbing a large mountain in a car or rising in an airplane? Why don’t your ear drums burst on the airplane?

The outside pressure changes more quickly than your ear can adjust which creates a pressure difference in pressure. When unbalanced pressures equalize, popping sensation within a small tube occurs.

13.1 Fluid Pressure

Why can an almost empty gasoline can in the garage be more dangerous than a full tank?

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A can containing a small amount of water is heated until the water boils. Then the can is capped. As the can cools, the pressure inside the can becomes less than the pressure outside the can. The difference in pressure crushes the can.


13.1 Fluid Pressure

Assessment Questions

1. A gymnast standing on one hand (area 0.02 m2) pushes down on the ground with a force of 600 N. How much pressure does the gymnast exert on the ground? a. 3000 Pa

b. 30,000 Pa

c. 12 Pa

d. 1200 Pa

13.1 Fluid Pressure


1. A gymnast standing on one hand (area 0.02 m2) pushes down on the ground with a force of 600 N. How much pressure does the gymnast exert on the ground? a. 3000 Pa

b. 30,000 Pa

c. 12 Pa

d. 1200 Pa

ANS: B

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2. The SI unit for pressure, equal to 1 N/m2, is called thea. atmosphere.b. foot-pound.c. pascal.d. watt.

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2. The SI unit for pressure, equal to 1 N/m2, is called thea. atmosphere.b. foot-pound.c. pascal.d. watt.

ANS: C

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3. The pressure exerted by a stationary fluid is determined by a. the area of surface containing the fluid and the type of

fluid.

b. the weight and volume of the fluid.

c. the type of fluid and its depth.

d. the shape of the container and the weight of the fluid.

13.1 Fluid Pressure


3. The pressure exerted by a stationary fluid is determined by a. the area of surface containing the fluid and the type of

fluid.

b. the weight and volume of the fluid.

c. the type of fluid and its depth.

d. the shape of the container and the weight of the fluid.

ANS: C

13.1 Fluid Pressure


4. Which of the following statements about fluid pressure is false? a. Pressure increases as depth increases.

b. The pressure at a given depth is constant.

c. The pressure in a fluid is exerted downward.

d. Liquids and gases exert pressure.

13.1 Fluid Pressure


4. Which of the following statements about fluid pressure is false? a. Pressure increases as depth increases.

b. The pressure at a given depth is constant.

c. The pressure in a fluid is exerted downward.

d. Liquids and gases exert pressure.

ANS: C

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5. Why do mountain climbers on very high peaks need cylinders of oxygen as they approach the summit?

a. The tops of the mountains extend out of the atmosphere.

b. The pressure of air decreases as altitude increases.

c. Air on the mountaintops is too cold to breathe.

d. Air pressure at high altitudes is too great for normal breathing.

13.1 Fluid Pressure


5. Why do mountain climbers on very high peaks need cylinders of oxygen as they approach the summit?

a. The tops of the mountains extend out of the atmosphere.

b. The pressure of air decreases as altitude increases.

c. Air on the mountaintops is too cold to breathe.

d. Air pressure at high altitudes is too great for normal breathing.

ANS: B

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Assignments:

CW: Finish & turn in station labs today. (station 8, 10 exception)

CW: Finish pendulum lab and turn in.

CW: Work on creating your egg drop device today. If your materials are not here tomorrow, you will lose points for the group...

HW/CW: Complete the 12 problems handout that was given out on Monday which is due tomorrow... (work on class only if all labs are completed or if you do not have your group materials.)

Note to me:Computer Quizhttp://www.phschool.com/Web code = cca-2120

check balloon lab in book pg. 383...look for momentum lab...

13.2 Forces and Pressure in Fluids

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