How do planes fly?
Have you ever wanted to fly or wondered how to fly? Picture this ... so you're sitting by a tree in the shade and this plane comes along. All of a sudden these questions come up in your head - how is it staying up in the air? How is it carrying so many people? HOW?!
Lift, weight, drag and thrust are all needed to fly a plane.
Lift is air turned by the plane. Lift holds a plane and a bird in the air. Lift is an aerodynamic, upward force produced by a difference in pressure due to airflow. Lift pulls a plane up to the sky. Lift needs to be greater than weight to get the object off the ground. Lift is a force that works in the opposite direction to weight.
Weight is a force due to gravity. Weight is generated by the gravitational pull of the earth. Weight is a force that works in the opposite direction to lift.
Drag is sometimes called air resistance or fluid resistance. Drag refers to forces that oppose the relative motion of an object through a fluid (a liquid or gas). Drag is a force that works in the opposite direction to thrust.
Thrust is the force that moves an object forward. For example, the thrust of the engines on an aeroplane keeps it moving through the air. Thrust needs to be greater than drag for forward movement. Thrust is a force that works in the opposite direction to drag.
Lift needs to be greater than weight but the planes still need to travel fast enough for the wings to work, and thrust must be greater than drag. An object needs an unbalanced force acted on it to change speed or direction. If you add more weight to the plane you would need more thrust and lift to get it off the ground and up into the air.
In conclusion lift and weight seem the same but they are completely different - lift wants to go up and weight wants to go down. It's the same as thrust and drag they are completely different - thrust wants to go forward and drag wants to slow the plane down.