Steps to this lesson:
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1. Read this page on Pressure. Take the time to record answers to questions (Reflecting Moments) posed as well as your thoughts on the videos. When you get to the bottom of the page. Transfer the answers from your notebook to the comment section. Please include your initials.
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2. Once you have completed review questions and you think you have a good understanding of the material, you may move onto the assignment. Read the instructions carefully and complete to the best of your ability. If you have any questions, make sure you ask! It doesnt hurt to ask!
Consider this : If you tried to hammer a bowling pin into the wall, nothing would probably happen except for people deciding to no longer lend you their bowling pins. However, if you hammer with the same force on a nail, the nail would be a lot more likely to penetrate the wall. This shows that sometimes just knowing the magnitude of the force isn't enough, you also have to know how that force is distributed on the surface of impact. For the nail, all the force between the wall and the nail was concentrated into the very small area on the sharp tip of the nail. However, for the bowling pin the area touching the wall was much larger, and therefore the force was much less concentrated.
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What is Pressure?
The force acting on a certain area of surface. The larger the force, the greater the pressure. The smaller the area, the greater the pressure. You can think of pressure like "collisions between molecules". When there is a fight or a collision, there is often force involved. The more collisions, the more force ; which means a higher pressure.
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Factors that Affect Pressure
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There are two factors that affect pressure
1. Volume : as the volume decreases in a space, the pressure will increase this is because there is less room for the molecules to move around. This increases the number of collisions between them and thus increases the pressure. The opposite is true as well. When there is a lower pressure, there is more volume for the molecules to occupy.
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2. Temperature : the temperature of molecules also affects the pressure. As the temperature gets warmer, particles move faster. This causes more collisions between molecules. The more collisions, the more force that is present. This means that the pressure increases. As with volume, the opposite is also true. When the temperature of a substance goes down, the molecules move a lot slower and have less collisions with one another. This decreases the force present which results in a lower pressure
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Calculating Pressure
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The unit for pressure is the Pascal (Pa) ï‚¢
You can determine pressure if you know the force and the area
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Example Problem #1 : An aquarium is filled with water that weighs 10 000N. If the base of the aquarium has an area of 1.6 m², what pressure does the water exert on its base?
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Answer :
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Example Problem #2 : If the atmospheric pressure is 101 200 Pa and you are holding your hand, the atmosphere is exerting a force on your hand. If the area of your palm is 0.006m², calculate the force on your hand.
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Answer :
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Example Problem #3 : The weight of water in a glass is 4.9 N. If the water is exerting a pressure of 1700 Pa on the bottom of the glass, what is the area of the bottom of the glass?
Answer :
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Who discovered Pressure?
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In the mid 1600's, the French mathematician Blaise Pascal was curious about how pressure was exerted in a fluid. He wondered what would happen if a force was applied to a fluid in a closed system. Through experimentation, he found that the force created pressure that was transmitted equally in all directions throughout the fluid. He developed a law of describe his observations.
Pascal's Law : an enclosed fluid transmits pressure equally in all directions.
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This law went on to explain concepts such as hydraulics devices and blood pressure .
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Application of Pressure
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Hydraulic and Pneumatic Systems
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Hydraulic System : The study of pressure in liquids. Hydraulic systems: devices that transmit applied force through a liquid to move something else.Hydraulic systems use liquids because they are incompressible (they cannot be squeezed into a smaller volume). The liquid must be enclosed in a tube or pipe. The pressure produced will exert in all directions equally. This pressure will cause motion at the other end of the hydraulic system
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Pneumatic System : A gas is used to exert a force on the gas in an enclosed space. Compressors are necessary as gases can be compressed. They build up air pressure. Increasing pressure of a fluid will decrease volume by the same amount.
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Blood Pressure
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Reflecting Moment : What do you think? Do you think the pressure we talk about in hydraulic systems is the same type of blood pressure we talk about in our bodies? Leave your thoughts in the box below. Please include a reasoning.