What is a force?

A force is an action exerted on an object that may change the object’s state of motion or rest. Force is measured in Newtons. A contact force comes in contact with the object (ex: friction, catching a ball, pulling a string). A field force acts at a distance (ex: electricity, static, gravity, magnetism). Force is a vector quantity. A vector is a physical quantity with both magnitude and direction.  The net force is the vector sum of all forces acting on a body. An external force is a single force that acts on a body. Net force is equivalent to one force that produces the same effects as all the forces acting on the body. 

        The four main aerodynamic forces applied to a rocket are weight, thrust, lift, and drag. Weight is the gravitational force on an object. It pulls the object directly towards the earth from the center of gravity. Thrust is an oppositional force to weight. It propels the rocket through the air. Lift is a force perpendicular to direction of motion. Lift does not have much affect on the flight of a rocket, but it is what propels an airplane. Drag is a force that opposes motion. It decreases with altitude.