1. Airplane forces

2. Weight and Lift WEIGHT – directed to the center of earth – airplane parts, fuel, and people, luggage or freight LIFT – generated by the motion of the plane – perpendicular to flight direction – generated by the wings

3. Drag DRAG – air friction that resists the forward motion – opposite of flight direction

4. Thrust THRUST – used to overcome drag – created by a propulsion system – direction depends of the position of the engines. Generally thrust is forward Thrust occurs due to Newton’s 3 rd Law – hot gasses rush out of the back of the engine and the plane is pushed forward

5. Airplane motion When all forces are balanced, the airplane will maintain a constant velocity (cruise control on a car) When the forces are unbalanced, the aircraft accelerates in the direction of the greatest force Acceleration of the aircraft is based on Newton’s 2 nd Law F=ma

6. Forces and motion

7. Unbalanced Forces If lift is more than weight the airplane will rise If lift and weight are equal the airplane will cruise If weight is greater than lift the airplane will descend

8. Questions 1. Define force 2. What are the four forces acting on a plane 3. How do each of the four forces act on an airplane in flight? (Which direction does each push or pull the aircraft?) 4. Define balanced and unbalanced forces 5. In terms of the airplane forces, what needs to happen so the forces are balanced? What what we call it when all four forces are balanced on an airplane?

9. Questions 6. You are traveling on an airplane and the pilot announces on the intercom that you have reached your cruising altitude of 32,000 feet. Explain what the pilot is telling you in terms of the forces. 7. During a flight when we are cruising at a specific altitude, the four forces are balanced. At what points during a flight are the forces unbalanced? 8. Define Newton’s First Law of Motion

10. Questions 9. In your own words, explain how Newton’s First Law of Motion explains the motion of a cruising airplane. 10. What are some ways the forces on an airplane can become unbalanced? (Name at least three)