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WHAT WILL HAPPEN IF CARS OR VEHICLES HAVE NO BRAKE SYSTEM?
“It can be stated as: “a change in pressure at one part of the liquid will be transmitted undiminished to the
other parts”.
PASCAL’S PRINCIPLE
is considered as one of the most useful application of liquid pressure.
As a driver steps on the gas pedal or brakes, the pressure of the brake fluid will cause the brake lining to be in contact with the rotating brake drum (wheel) thus producing a braking force.
APPLICATION of the pascal’s principle
Car brake system
Hydraulic lift helps automechanic lift heavy automobiles & other heavy materials
Hospital bed, dentist’s chair, barber’s chair
APPLICATION of the pascal’s principle
WHY DO SHIPS & SWIMMERS FLOAT & DO NOT SINK?
ARCHIMEDES PRINCIPLE
“An immersed ( partially or completely ) body is buoyed up or is pushed upward by a force equal to the weight of the fluid it displaces”.
The force that pushes bodies upward in order to float is the BUOYANT FORCE.
Ships do not sink because it displaces an amount of water equal to its weight.
APPLICATION of the Archimedes principle
Thus, a swimmer do not sink because of buoyancy.
His greatest contributions to mathematics were in the area of Geometry. He was believed to have been obsessed with Geometry though.
He is believed to be one of the three greatest mathematicians along with Isaac Newton and Carl Gauss.
ARCHIMEDES
287 BC – 212 BC
Archimedes was also an accomplished engineer and an inventor.
Discovered how to find the volume of a sphere & determined the exact value of Pi.
CONTRIBUTIONS
Principle of Buoyancy. (It is believe that when he discovered the principle of Buoyancy, he went running through the streets naked shouting 'Eureka' - I have found it)
It is also believed that he was actually the first to have invented integral calculus, 2000 years before Newton and Leibniz. Powers of Ten as well as Scientific Notation).
CONTRIBUTIONS
HOW DO WE CALCULATE BUOYANT FORCE?
Buoyant Force (BF) = mass of the displaced liquid (kg) x g = Weight of displaced liquid
Buoyant Force = Weight in Air – Weight in Water
Weight in Air – Weight in Water = Loss of Weight in water
Problems!
1. An object weighs 10.5 Newtons in air. When immersed in water, it weighed 9.8 Newtons. What is the loss of weight of the object? How much is the buoyant force exerted by the water to the object?
2. A man weighs 392 Newtons in air. If he is in water his weight decreases by 7 Newtons. How much is the buoyant force exerted on the man? What is the weight of man in water?
3. A man whose mass is 50kg dives into a pool. How much buoyant force did he exert?
Other Application: Ships, submarines, balloons
Hot air balloons is buoyed up or is acted upon by an upward force. Hot air is less dense than cold air.
WHAT IS BLOOD PRESSURE?
Blood Pressure is:
the pressure of blood within the arteries of the body.
the driving force that causes blood to flow through the body from the arteries (where the pressure is high), through organs, and into the veins (where the pressure is low).
Source:http://images.search.yahoo.com/search/images?_adv_prop=images&imgsz=all&imgc=&vf=all&va=arteries&fr=FP-tab-web-t500&ei=UTF-8
Cross-sectional image of an artery
BP is also known as arterial blood pressure.
There is high pressure in the arteries
Blood pressure is the pressure exerted by the blood on the walls of the blood vessels.
Source:http://images.search.yahoo.com/search/images?p=BLOOD+VESSELS&ei=UTF-8&fr=FP-tab-web-t500&x=wrt
There is low pressure in the arteries
is the pressure in the arteries as the muscle of the heart contracts & pumps blood into the arteries.
Systolic blood pressure
Diastolic blood pressure
is the pressure in the arteries as the muscle of the heart relaxes after it contracts.
TYPES OF BLOOD PRESSURE
Typical values for the arterial blood pressure of a resting, healthy adult are approximately 120 mmHg systolic and 80 mmHg diastolic (conventional)
Systolic blood pressure for most healthy adults falls between 90 and 120 millimeters of mercury (mm Hg). Normal diastolic blood pressure falls between 60 and 80 mm Hg.
BLOOD PRESSURE
According to studies, normal BP is now lower than 120/80. BP between 120/80 & 140/90, used to be considered “pre-hypertension,” now are considered too high.
BLOOD PRESSURE
Categories for Blood Pressure Levels in Adults
(Ages 18 Years and Older)
Blood Pressure Level (mmHg)
Category Systolic Diastolic
Normal < 120 and < 80
Prehypertension 120-139 or 80-89
High Blood Pressure
Stage 1 Hypertension
140–159 or 90–99
Stage 2 Hypertension
160 or 100
What is high blood pressure?
High blood pressure, also called hypertension, is, simply, elevated pressure of the blood in the arteries.
It results from two major factors:
The heart pumps blood with excessive force (F)
The body's smaller blood vessels (arterioles) narrow (Area), so that blood flow exerts more pressure against the vessels' walls.
What happens to the blood vessels in hypertension?
As blood vessels narrow (decrease in area), the higher the resistance (higher pressure) to the blood flow, thus resulting to higher the blood pressure.
Resistance is related to size (The larger the blood vessel, the lower the resistance), The smaller the surface area, the greater is the resistance.
All level of blood pressure puts mechanical stress on the arterial walls.
What happens to blood pressure as we grow old?
Smoothness is reduced by the buildup of fatty deposits on the arterial walls.
The arteries become inelastic or they loss their elasticity.
What happens to blood pressure as we grow old?
What are the most common effects of Hypertension?
High systolic BP appears to be a significant indicator for heart complications (87% between 50 & 59).
High diastolic BP is a strong predictor of heart attack and stroke in young adults and in people of any age. It can also cause hardening of the arteries.
Source:http://www.reutershealth.com/wellconnected/doc14.html
Although the body can tolerate increased blood pressure for months & even years, eventually the heart may enlarge (hypertrophy), which is a major factor in heart failure which can also injure blood vessels in the heart, kidneys, the brain, and the eyes.
What are the most common effects of Hypertension?
What is low blood pressure?
Low blood pressure is blood pressure that is so low that it is causing symptoms or signs due to the low flow of blood through the arteries and veins. It is also known as hypotension.
Common Effects of Hypotension
When blood flow is too low to deliver enough oxygen & nutrients to vital organs such as the brain, heart, and kidney; the organs do not function normally and may be permanently damaged.
If there is insufficient blood flow to the brain, brain cells do not receive enough oxygen & nutrients, and a person can feel light-headed, dizzy, or even faint.
When there is insufficient blood pressure to deliver blood to the coronary arteries (the arteries that supply blood to the heart’s muscle), a person can develop chest pain (angina) or even a heart attack.
When insufficient blood is delivered to the kidneys, the kidneys fail to eliminate wastes from the body, for example, urea and creatinine.
Common Effects of Hypotension
Air pressure is the force exerted on you by the weight of tiny particles of air (air molecules).
Air molecules are invisible, they still have weight and take up space. Since there's a lot of "empty" space between air molecules, air can be compressed to fit in a smaller volume.
Atmospheric pressure is the pressure above any area in the Earth's atmosphere caused by the weight of air.
Weather forecasters measure air or atmospheric pressure with a barometer. It is also used to monitor weather conditions.
Barometers are used to measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb).
Low pressure Area
is a region where the atmospheric pressure is lowest in relation to the surrounding area. Tropical storms, extratropical cyclones, deppressions etc.
Source: http://en.wikipedia.org/wiki/High_pressure_area
Low pressure forms at the Intertropical convergence zone (ITCZ),
Low pressure area results to stronger winds and atmospheric lift. It produces cloud cover, the air becomes saturated & brings cloudy or overcast skies & lower temperature. It is gives bad or rainy weather condition.
Low pressure Area
High pressure Area
is a region where the atmospheric pressure is greater than the surrounding area. In some countries, these may be referred to as anticyclones.
It is associated with light winds & clear skies. During the day, since no clouds are present to reflect sunlight, there is more incoming shortwave solar radiation and temperatures are higher. It is also yields fair weather condition.
What is the relationship of pressure & temperature?
What is the relationship of pressure & altitude?
Pressure is directly proportional to Temperature
Pressure is inversely proportional to Altitude
The pressure under water increases with depth, a fact well known to scuba divers. At a depth of 10 m under water, pressure is twice the atmospheric pressure at sea level, and increases by 100 kPa for every extra 10 m of depth.
OTHER FACTS ABOUT PRESSURE
On the other hand, atmospheric pressure diminishes with height, a fact first verified on the Puy-de-Dôme and the Saint-Jacques Tower in Paris, on the instigation of Blaise Pascal himself. As the atmosphere gets lighter with height, the atmospheric pressure varies exponentially with height.
e.g. artesian wells, water towers, dams
OTHER FACTS ABOUT PRESSURE
Why do my ears pop? If you've ever been to the top of a tall mountain, you may have noticed that your ears pop and you need to breathe more often than when you're at sea level.
OTHER APPLICATION
As the number of molecules of air around you decreases, the air pressure decreases. Your ears pop in order to balance the pressure between the outside & inside of your ear.
You are breathing fewer molecules of oxygen, you need to breathe faster to bring the few molecules there are into your lungs to make up for the deficit.
Barometers are used to measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb).
A measurement of 29.92 inches of mercury is equivalent to 1013.25 millibars.
Exercise 14: pressure
1. Find the pressure exerted by a 110-N wooden block on a surface The surface is 2 meters long & 0.98 m wide.
2. The area of a surface is 5 m2. If a 70-N body is in contact with the surface then how much PRESSURE is exerted on it?
3. The radius of a circular block on a surface is 2 meters. A 250-N baggage was placed on top of the surface, find the pressure exerted.
4. The pressure exerted by a wooden block on a surface is 50 pascals. If the area of the block is 1.5m2 then how heavy is the block?
5. Find the weight of a baggage which is in contact with a surface which is 2 meters long & 0.98 m wide. The pressure exerted on the surface is 35 N/m2.
6. Find the pressure of seawater with an altitude of 100 meters.
7. Find the altitude at which freshwater will have a pressure of 100 pascals.
8. Find the density of a liquid which exerts a pressure of 65 pa in an altitude of 50 meters.
HAVE A NICE DAY!
