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

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

Pressure How is pressure calculated? To calculate pressure, divide the force by the area over which the force acts.

Pressure is the result of a force distributed over an area.
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)

Pressure 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 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 in Fluids How does water pressure change with depth? How is pressure distributed at a given level in a fluid?

Pressure in Fluids 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.

A fluid is a substance that assumes the shape of its container.
Pressure in Fluids 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 Particles in a liquid are tightly packed together but are able to slide past one another.

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

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

Planetary Atmospheres
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.

Exploring Boiling Points of Chlorocarbons
Interpreting Tables Which planet listed in the table has the greatest atmospheric pressure?

Exploring Boiling Points of Chlorocarbons
Interpreting Tables Which planet listed in the table has the greatest atmospheric pressure? Answer: Venus, 9120 kPa

Exploring Boiling Points of Chlorocarbons
Interpreting Tables What chemical substance exists in all but one of the atmospheres?

Exploring Boiling Points of Chlorocarbons
Interpreting Tables What chemical substance exists in all but one of the atmospheres? Answer: Nitrogen

Exploring Boiling Points of Chlorocarbons
Converting Units The bar is another unit of pressure (1 bar = kPa). Convert each of the given pressures into bars.

Exploring Boiling Points of Chlorocarbons
Converting Units The bar is another unit of pressure (1 bar = kPa). Convert each of the given pressures into bars. Answer: Mercury, 10–15 bar; Earth, 1 bar; Venus, 90.0 bar; Mars, bar

Exploring Boiling Points of Chlorocarbons
Using Formulas How much force is exerted on a square-meter area of Venus’s surface?

Exploring Boiling Points of Chlorocarbons
Using Formulas How much force is exerted on a 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 = × 107 N

Exploring Boiling Points of Chlorocarbons
Predicting On which planet would a balloon filled with a given quantity of helium have the smallest volume?

Exploring Boiling Points of Chlorocarbons
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.

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

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

Air Pressure and the Atmosphere
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.

Air Pressure and the Atmosphere
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.

Air Pressure and the Atmosphere
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.

Air Pressure and the Atmosphere
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.

Air Pressure and the Atmosphere
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.

Assessment Questions 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? 3000 Pa 30,000 Pa 12 Pa 1200 Pa

Assessment Questions 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? 3000 Pa 30,000 Pa 12 Pa 1200 Pa ANS: B

The SI unit for pressure, equal to 1 N/m2, is called the
Assessment Questions The SI unit for pressure, equal to 1 N/m2, is called the atmosphere. foot-pound. pascal. watt.

The SI unit for pressure, equal to 1 N/m2, is called the
Assessment Questions The SI unit for pressure, equal to 1 N/m2, is called the atmosphere. foot-pound. pascal. watt. ANS: C

The pressure exerted by a stationary fluid is determined by
Assessment Questions The pressure exerted by a stationary fluid is determined by the area of surface containing the fluid and the type of fluid. the weight and volume of the fluid. the type of fluid and its depth. the shape of the container and the weight of the fluid.

The pressure exerted by a stationary fluid is determined by
Assessment Questions The pressure exerted by a stationary fluid is determined by the area of surface containing the fluid and the type of fluid. the weight and volume of the fluid. the type of fluid and its depth. the shape of the container and the weight of the fluid. ANS: C

Which of the following statements about fluid pressure is false?
Assessment Questions Which of the following statements about fluid pressure is false? Pressure increases as depth increases. The pressure at a given depth is constant. The pressure in a fluid is exerted downward. Liquids and gases exert pressure.

Which of the following statements about fluid pressure is false?
Assessment Questions Which of the following statements about fluid pressure is false? Pressure increases as depth increases. The pressure at a given depth is constant. The pressure in a fluid is exerted downward. Liquids and gases exert pressure. ANS: C

Assessment Questions Why do mountain climbers on very high peaks need cylinders of oxygen as they approach the summit? The tops of the mountains extend out of the atmosphere. The pressure of air decreases as altitude increases. Air on the mountaintops is too cold to breathe. Air pressure at high altitudes is too great for normal breathing.

Assessment Questions Why do mountain climbers on very high peaks need cylinders of oxygen as they approach the summit? The tops of the mountains extend out of the atmosphere. The pressure of air decreases as altitude increases. Air on the mountaintops is too cold to breathe. Air pressure at high altitudes is too great for normal breathing.ANS: B

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