IELTS READING LEVEL 6.5 – How Do Airplanes Fly?

How Do Airplanes Fly?

by Dr. Hany Farid

When an airplane is in flight, there is a downward force (gravity) and an upward force (lift) acting on the airplane. As an airplane moves through the air, the shape of the wings causes there to be less air pressure pushing down on the wings than pushing up on the wings. This difference in pressure yields the upward lift. If the downward gravitational force is less than the upward lift, then the airplane stays in the air. Read on for a more detailed explanation.

Fact 1. As an airplane’s propellers spin, they give the airplane a forward force (thrust). As the airplane moves forward there is a backward force (drag) caused by the resistance of the air.

 

Fact 2. An airplane is attracted downward due to gravity. This force increases with the mass (weight) of the object.

 

Fact 3. As an airplane moves forward, the shape of its wing creates lower pressure above the wing than below, yielding a net upward force known as lift.

 

As an airplane speeds along the runway, the airplane’s wings disrupt the flow of the air. This disruption causes the air above the wings to move faster than below the wings. As a result, the air pressure above the wing is less than below the wing. As the airplane speeds up, this pressure difference increases until the lift is stronger than the gravitational force, and the airplane takes off. In order to remain in flight, the thrust must be greater than the drag, and lift must be greater than the force of gravity.

There is still some debate as to the exact cause of the difference in the air’s speed around the wings. The basic concept described here, however, seems to explain why an airplane can fly.


Vocabulary

 

disrupt       dis ·rupt

Advanced Definition

transitive verb

  1. to throw into disorder or turmoil.

An explosion disrupted the peaceful demonstration.

  1. to interrupt or break off, usually temporarily.

Hecklers disrupted the governor’s speech.

These are some examples of how the word or forms of the word are used:

  1. Those substances can disrupt the body’s hormone balance.
  2. Kidney stones cause pain when they disrupt urine flow (which can cause infection).
  3. The entire class listened to their teacher in silence, afraid to disrupt the atmosphere of the ancient temple.
  4. Recent studies show that chemicals called phthalates, which may disrupt hormones, can seep into bottled water from the plastic container.
  5. That’s why we must always be careful to take care of the environment-the earth’s temperature is carefully maintained by specific mechanisms. We sure wouldn’t want todisrupt them!

 

force       force

Definition

noun

  1. power, energy, or physical strength.

The force of the wind knocked down the trees.

  1. a group of people with a common goal or activity.

She is a member of the police force.

verb

  1. to make or cause to do something by using strength or power.

Ivan forced her to tell the truth.

Advanced Definition

noun

  1. active power, energy, or physical strength.

The force of the hurricane knocked down the trees.

  1. the use of such power, energy, or strength.

The enemy took the castle by force.

  1. someone or something with the capacity to influence or cause change.

The force of logic eventually convinced the committee.

A group of parents was the main force behind the change in the town’s speed limit.

She believed that, as a politician, she could be a force for good.

  1. in law, illegal violence, as against a person.

Accidental death was ruled out, as use of force on the victim was apparent.

  1. a group of people joined by a common goal or activity.

the labor force

the police force

  1. in physics, an influence on the shape, motion, or other characteristics of a body or system.
  2. (often pl.) military troops; army.

The enemy has overpowered our forces in the area.

  1. effective intensity, as of the mind.

transitive verb

  1. to use strength or coercion in order to compel.

The interrogators forced him to tell the truth.

  1. to cause to do something despite resistance or hesitation.

The accident forced her to rely on her family for help.

Being turned down for promotion forced him to make a difficult decision.

  1. to bring about (something) despite there being reluctance or unwillingness.

The scandal forced the congressman’s resignation from office.

Complaints from customers forced the removal of the product from the market.

  1. to obtain through force.

His captors forced a confession from him.

  1. to tax or strain.

Don’t force the situation.

These are some examples of how the word or forms of the word are used:

  1. Darwin realized that the birds had grown beaks specialized for their environment because nature had forced them (to) over many generations.
  2. In an actual launch, astronauts feel about three times the force of gravity. Gravity is the force that pulls things toward Earth.
  3. Electromagnetic force is the interaction responsible for almost everything in daily life. Magnets are objects that produce an area of magnetic force called a magnetic field.
  4. Mom grabbed the end of one, and I held the handle on the other; and we yanked. The buckets slid free, and I fell over from the force of the pull.
  5. Kinetic energy is a term related to physics that describes the energy an object possesses due to motion. Measuring an object’s kinetic energy means measuring the amount oforce an object needs to accelerate.
  6. There is a vitality, a life force, an energy, a quickening that is translated through you into action, and because there is only one of you in all of time, this expression is unique.

 


Name: ___________________________________ Date: _______________
Comprehension Questions
1. What is the downward force that acts on an airplane in flight?
A. lift
B. drag
C. thrust
D. gravity
2. As an airplane moves forward, the shape of its wings causes a difference in pressure below and above the wings. What is the effect of this difference in pressure?
A. a downward force is created
B. the airplane speeds up
C. an upward force is created
D. the airplane slows down
3. Read these sentences from the text.
“As an airplane’s propellers spin, they give the airplane a forward force (thrust). […] As an airplane moves forward, the shape of its wing creates lower pressure above the wing than below, yielding a net upward force known as lift.”
Based on this evidence, what conclusion can be drawn about thrust and lift?
A. Airplanes do not need lift to fly, as long as they have thrust.
B. Airplanes need lift in order to create thrust.
C. Airplanes can create lift without any thrust.
D. Airplanes need thrust in order to create lift.
4. Which of the following would probably help an airplane to take off and remain in flight?
A. having a large body and small wings
B. moving at a slow speed while on the ground
C. being made from a lightweight material
D. carrying heavy luggage inside the plane
5. What is the main idea of this text?
A. Airplanes fly as a result of the forward force of thrust being greater than the backward force of drag.
B. The upward force called lift is caused by a difference in air pressure above and below an airplane’s wings.
C. Four different forces called thrust, drag, lift, and gravity, all prevent airplanes from being able to fly.
D. Airplanes fly as a result of the upward force of lift being greater than the downward force of gravity.
6. Why might the author have chosen to include three diagrams in this text?
A. to illustrate the forces being discussed
B. to introduce new information into the text
C. to give examples of how different planes fly
D. to provide an alternate explanation of how planes fly
7. Choose the answer that best completes the sentence below.
As an airplane speeds along the runway, the airplane’s wings disrupt the flow of the air.
____, the air above the wings moves faster than below the wings.
A. However
B. As a result
C. For instance
D. Previously
8. What gives an airplane a forward force?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
9. An airplane takes off when the upward force beneath its wings is greater than the downward force of gravity. Starting from when the airplane is standing still, describe the sequence of events that has to happen for the upward force to become greater than the downward force of gravity.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
10. An airplane would not be able to fly if it did not have a propeller. Why not? Support your answer with evidence from the text.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

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