How does an airplane fly?

Skip to Activity! How does an airplane fly? Grade 8: Topic Choice 1 We all know that an airplane is heavier than air, so how does that 500,000 pound metal object fly? Next Skip to Quiz

The answer is FORCE Skip to Activity! Remember, Force = mass x acceleration, and is the capacity to do work or cause change It actually has real applications, and explains how an airplane can fly! Back Next Skip to Quiz

Four Forces Affecting an Airplane in Flight Skip to Activity! Click on a force to learn more about it When forces are balanced, the airplane is moving at a constant speed and altitude. If we change any force, we change the motion of the aircraft. Back Next Skip to Quiz

Lift • Lift is the force that pushes an airplane up into the air • It is caused by the shape of an airplane’s wings, and the air flowing over the wing. • Lift is the most complex of the 4 forces because it cannot be created without forward motion of the airplane. Next Force Menu Skip to Quiz

How do we create lift? • Picture the air going over the wing as paired particles. 2 airflow front back 2 1 Notice the distance the red partner has to travel from 1 to 2 versus the distance the blue partner travels Back Next Force Menu Skip to Quiz

The particles going over the top of the wing (red) have to travel a further distance than their partners (blue) on the bottom of the wing. • This means the air on top of the wing is moving faster than the air on the bottom of the wing because speed = distance/time Fast moving air = less pressure Slow moving air = more pressure Increased pressure on the bottom of the wing and decreased pressure on the top of the wing creates LIFT Back Next Force Menu Skip to Quiz

Lift If we increase lift, Drag Thrust Weight the plane will go up, or ascend/climb. Back Next Force Menu Skip to Quiz

Lift If we decrease lift, Drag Thrust Weight the plane will go down, or descend. Back Next Force Menu Skip to Quiz

How might we change lift? (Click screen to find out) • Change the angle of the wing to change the airflow pattern. • Increase speed to increase the airflow over the wing, further decreasing the pressure above the wing, and increasing lift. Back Next Force Menu Skip to Quiz

Thrust • Thrust is the force that pushes an airplane forward • It is produced by propellers or jet engines Next Force Menu Skip to Quiz

Lift If we increase thrust, Thrust Drag Weight the plane will speed up, or accelerate. Back Next Force Menu Skip to Quiz

Lift If we decrease thrust, Thrust Drag Weight the plane will slow down, or decelerate. Back Next Force Menu Skip to Quiz

How might we change thrust? (Click screen to find out) • Increase power, and therefore speed (accelerate) • Decrease power, and therefore speed (decelerate) Back Next Force Menu Skip to Quiz

Drag • Drag is the force that slows the airplane down • It is similar to friction Next Force Menu Skip to Quiz

Lift If we increase drag, Thrust Drag Weight the plane will slow down, or decelerate. Back Next Force Menu Skip to Quiz

Lift If we decrease drag, Thrust Drag Weight the plane will speed up, or accelerate. Back Next Force Menu Skip to Quiz

How might we change drag? (Click screen to find out) • Change the shape of the wing to interfere with airflow • Put landing gear down, which will interfere with airflow and slow the plane down. Back Next Force Menu Skip to Quiz

Weight • Weight is the force of a mass being attracted to another mass • With airplanes, this force is the mass of the plane times acceleration, in this case, gravity Next Force Menu Skip to Quiz

Lift If we increase weight, Thrust Drag Weight the plane will go down, or descend. Back Next Force Menu Skip to Quiz

Lift If we decrease weight, Drag Thrust Weight the plane will go up, or climb/ascend. Back Next Force Menu Skip to Quiz

How might we change weight? (Click screen to find out) • Add cargo or passengers to increase weight • Is this something we can do in flight? • Decrease cargo or passengers to decrease weight. • Think skydiving or food/supply drops Back Next Force Menu Skip to Quiz

Skip to Activity! Remember how balanced forces do not cause a change in motion? How do the forces affecting an airplane balance? What are the pairs of opposite forces? (Click screen for answer) • Lift and Weight • Thrust and Drag If the forces are balanced, the airplane is no longer changing speeds or altitudes (height from the ground). It is cruising at a constant speed and altitude until one of these forces is manipulated. Back Next Force Menu Skip to Quiz

Skip to Activity! When discussing these forces on airplanes, they are somewhat intertwined and not as clear cut as previously presented. However, for this lesson we have been, and will continue to, focus on the primary reaction to increasing or decreasing the four forces. Just to introduce the idea: • Lift is a more complex force and one that can only be created by wind/air going over the wing. • This means that thrust must be occurring in order to produce lift. • As the plane accelerates (increased thrust), lift increases as well because air is moving faster over the wing, creating a lower pressure above the wing and therefore increased lift. Back Next Force Menu Skip to Quiz

Let’s Play! Activity! Click the purple arrows to increase or decrease the force and see what happens! Lift Drag Thrust Weight Back Force Menu Skip to Quiz

Increase Lift Next

Decrease Lift Next

Increase Weight Next

Decrease Weight Next

Increase Thrust Next

Decrease Thrust Next

Increase Drag Next

Decrease Drag Next

Quiz • If you are ready to take the quiz, click • In the quiz, click on your answer choice to see if you are correct. • If you would like more review, click Next Force Menu

Question 1 The four forces acting on an airplane are _____________________. • lift, gravity, drag, friction • drag, thrust, gravity, climb • lift, thrust, weight, drag • lift, friction, gravity, weight

Correct! Great Work! Next

Try again…that was a tough one Next

Question 2 Which force could be increased to result in the airplane descending? • Lift • Drag • Weight • Thrust

Question 3 If you decrease thrust, what will happen to the airplane? • Speed up (accelerate) • Slow down (decelerate) • Climb (ascend) • Descend

Question 4 Which forces must be equal and opposite to balance an airplane? • Drag & Weight, Lift & Thrust • Lift & Drag, Thrust & Weight • Lift & Weight, Thrust & Drag

YOU ARE FINISHED!!! You are now ready to move on to more complex force applications for airplanes! Next time someone asks how or why an airplane can fly…you have the answer! DONE!

How does an airplane fly?