The four forces are lift, weight, thrust, and drag. Lift is the force that holds the plane up and is generated by the wings. Weight is the force of gravity pulling the plane down. Thrust is the force produced by the engines that propels the plane forward. Drag is the force that opposes the motion of the plane and is caused by air resistance.
The shape of the wings, specifically the airfoil shape, determines the amount of lift that can be generated. A curved or cambered airfoil shape creates a pressure difference between the top and bottom of the wing, resulting in lift. Different wing shapes also affect the plane's stability and maneuverability.
The pilot uses the control surfaces, such as the ailerons, elevators, and rudder, to manipulate the four forces during flight. By adjusting the control surfaces, the pilot can change the direction, speed, and altitude of the plane.
At higher altitudes, the air is thinner and creates less lift. This means the plane needs to fly faster to generate enough lift to stay in the air. Additionally, drag is reduced at higher altitudes due to the lower air density, making it easier for the plane to maintain its speed.
The four forces can be affected by various factors such as air density, wind speed and direction, weight and balance of the plane, and the angle of attack of the wings. Changes in these factors can impact the lift, weight, thrust, and drag of the plane, requiring adjustments from the pilot to maintain control.