The fascination with flight has been the fuel that has motivated notable scientists and inventors to learn about aerodynamics for hundreds of years. Sir Isaac Newton devised and shared his three laws of motion in 1686, which focused on how objects move and the forces that affect movement. Scientists and inventors have also engaged in examination of the physics of flight to understand how birds fly and to apply these fundamentals to developing and honing aircraft flight. The physics of flight explain how airplanes leave the ground and land again safely and how birds soar through the sky.

Basic Flight Physics

Newton's three laws of motion include the following principles. The first law states that every object in motion will remain in motion unless some type of external force changes this. The second law of motion focuses on an object's mass and how it affects its acceleration. In short, the more mass that is in an object, the more force will be required to change its speed and/or direction. The third law states that every force has an opposing force that is of equal strength. Slowing or stopping a moving object requires the application of an opposite force.

Daniel Bernoulli was a Swiss scientist who lived during the 18th century. Bernoulli's contribution to flight physics centers around the discovery of the decreased pressure of fluid as velocity increases. The Bernoulli Principle is a foundational principle of aerodynamics.

Aerodynamics involves a combination of four different forces: lift, weight, drag, and thrust. Lift is the opposite force of weight, and it occurs as air moves on wings. The weight force includes the total weight of an object: The force of gravity naturally pulls weight down. Drag is a slowing force, opposite to the thrust force, which happens with the disruption of airflow. Thrust is a forward-moving force that opposes drag. Thrust happens due to the energy produced by the rotor or propeller.
For an airplane to fly, the four forces have to have the right balance. Taking off requires a stronger thrust than drag, and landing requires reduced thrust and lift to bring the plane back down to the ground. Airplane wings are an important component of lift due to the difference in air pressure on the top surface as compared to the under surface as a plane flies. This difference causes the airplane to go up. Helicopters also use the same forces for flight. Rotor blades are counterparts of an airplane's wings, providing lift for the helicopter. The difference is that helicopter rotor blades rotate, which forces air over them to give lift to the helicopter. Rockets are another common type of aircraft that also relies on the same four forces. Rockets use fuel to propel them into space. The rocket's engine exhaust also helps move it because the exhaust moves backward, which forces the rocket forward. Even kites fly using the forces of motion. Wind moving across the kite's sail produces pressure, which gives the kite lift. This pressure also creates a type of vacuum that produces thrust.
Birds take to the air using the same aerodynamic forces that make it possible for airplanes, helicopters, rockets, and kites to fly. Pressure on top of a bird's wings compared to below them creates an upward lift. When birds flap their wings, they create thrust to propel them through the air. Some birds glide and soar through the air by holding their wings at a V-shaped angle to control how the wind hits their wings. Birds' tails also help them control flight elevation and speed. By spreading out their tail feathers, drag occurs, which slows them down for landing.