E6B CTO 7 Pressure

With Al-Hilal leading 3–2 late in the match, Al-Ittihad equalized the score with a goal from the corner. The final score was 3–3.

equalized means:

• took the lead

• won

• made equal

• lost

It was the young student’s hope to become a doctor. However, after one year at the university, he realized that he did not have the desire to study three more years there and then four additional years at medical school. Therefore, he quit his studies and went to work for a construction company.

realized means:

• intended

• wondered

• hoped

• understood

In 1968, the Olympics were held in Mexico City, which is over 2,000 meters above sea level. At a high elevation, there is less oxygen in the air than there is at sea level. As a result, Olympic athletes had to train in mountainous areas to build up their lungs and get used to a lower amount of oxygen in the air.

elevation means:

• the amount of oxygen in the air

• the height above sea level

• a mountainous area

• an area with a large population

After Faiz’s management training period ended at the bank’s headquarters in Riyadh, he was sent temporarily to the Al-Khobar office to work as a regional manager. He was told his job in Al-Khobar would last for only three months.

temporarily means:

• permanently

• for a long time

• for a short time

• exactly

In a dental checkup, taking X rays of a patient’s teeth normally precedes the examination. The dentist needs to look at the X rays before he examines the patient’s teeth. The X rays can indicate tooth decay and other problems that he would be unable to find using his regular dental tools.

precedes means:

• examines

• requires

• comes before

• comes after

Peter Jennings never finished high school, yet he became very famous for his work in TV news. He compensated for his lack of education by teaching himself, taking a great interest in things, traveling, and thinking a lot about his experiences.

compensated means:

• adjusted for

• improved

• changed

• increased

If the mercury in a common thermometer were not confined to a glass tube, it would evaporate. confined means:

• poured in

• directed

• enclosed

• released

The fundamental idea behind the invention of the wheel is that things roll more easily than they slide. That is because there is less friction on a rolling object than on a sliding object.

fundamental means:

• useful

• dependent

• regular

• basic

Pressure is the force that is applied to the unit area of a surface by a gas, liquid, or solid. The greater the force, the greater the pressure.

One of the most common examples of pressure is atmospheric, or air, pressure. Air pressure is the force exerted by the weight of air from the top of the atmosphere as it presses down upon the layers of air below it. At sea level, the earth’s atmosphere presses against us with a force of almost one kilogram per square centimeter. Fortunately, we have air inside our bodies which equalizes the air pressure outside. Otherwise, our bodies would be crushed by the force.

Air pressure at sea level is what we are used to, so we might not realize that air pressure acts upon us all the time. If, however, you go to the top of a high mountain or ride in an airplane, you will notice the effect of the decrease in air pressure at higher elevations. The lower air pressure, of course, is the result of less air pressing down from above. As you go higher up, your ears will temporarily “pop,”or click, as your body adjusts to the reduced pressure. You will also need to breathe faster to adjust to the smaller amounts of oxygen present at higher altitudes.

Atmospheric pressure plays an important part in our daily lives. For example, wind is the movement of air from a point of high pressure to a point of low pressure. Also, pressure changes precede changes in the weather, like the coming of storms. Barometers are instruments that can alert us to storms by measuring such changes.

Changes in air pressure also change the boiling point of water. The boiling point is the temperature at which the pressure of steam is equal to the atmospheric pressure. At sea level, the two pressures are equal at 100°C. As the height above sea level increases, the air pressure and the boiling point of water become lower. Therefore, foods that are boiled at high altitudes cook at a lower temperature. To compensate for the lower boiling point, the cooking time must be increased.

Another important kind of pressure, which has many practical uses, is that of compressed air and other gases. The tires of your car, for example, contain air that is compressed at high pressure. Because their molecules are far apart, air and other gases can be easily squeezed into a smaller volume. The amount of pressure on a gas determines its volume. The greater the pressure on a gas, the smaller its volume. An oxygen tank used for underwater diving, for example, has the amount of a whole roomful of air (about45kg) compressed into it and is good for one hour of breathing.

Compressed air is very useful in refineries and other hydrocarbon processing plants. Saudi Aramco uses compressed air to operate machines, turbines, and the various instruments and gauges which control plant processes.

A final kind of pressure, hydraulic pressure, is one that is exerted by water or other liquids. Hydraulics is the study of the flow of fluids and how they can be used in machines in order to multiply force from a smaller to a larger area. Power can be transmitted by pushing on a confined liquid. Since the liquid will not compress, movement at one end of the confined area must result in movement at the other end. The transmission of force by an incompressible fluid is the fundamental idea of hydraulics.

The most common application of hydraulic pressure is the brake system in most passenger cars. When you press your foot on the brake pedal in a car, it pushes a piston. The piston creates high pressure in a pipe filled with an oily fluid, called brake fluid. At the other end of the pipe, the pressure pushes the brake shoes against the wheel. The friction caused by the brake shoe pressing against the wheel makes the wheel stop.

The main idea of the article is that _____.

• atmospheric pressure is produced by the weight of air

• compressed air has many uses in industry

• hydraulic pressure depends on the transmission of force by an incompressible fluid

• all types of pressure concern force that is applied by a gas, liquid, or solid

Atmospheric pressure plays an important part in our daily lives. For example, wind is the movement of air from a point of high pressure to a point of low pressure. Also, pressure changes precede changes in the weather, like the coming of storms. Barometers are instruments that can alert us to storms by measuring such changes.

A barometer is used to measure _____.

• air temperature

• changes in atmospheric pressure

• air pressure in car tires

• the boiling point of water