### force:

Normal force
* are forces which act perpendicularly to surfaces
  - where they are important in industrial situations
* contact force.
* is directly dependent upon the elastic modulus
  - equal to the force exerting on it perpendicularly
* is the force at which one surface is being pushed into another
  - pressing two surfaces together
* refers to the amount of force use to counteract the force of gravity.

Nuclear force
* form the basis for our comprehension of nuclear structure and reactions.
* overcome repulsion.

Opposite force
* Most opposite forces produce torque.
* Some opposite forces cause motion.

Physical force
* Some physical forces alter distribution.
* has no value where there is nothing else.

Positive force
* are forces in the positive direction i.e. repulsive forces.
* corresponds to repulsion.

Propulsion
* deals with heat transfer and effects of heat on flows.
* is acts
  - an act
  - by means of an interior mass
  - provided by the primary feathers, which are the outermost feathers in the wings
* is the means by which a projectile propels itself from one place to another
  - study of what kind of engine and power an airplane needs
* means to push forward or drive an object forward.
* moves things like spacecraft or jet planes forward by pushing something out of the back.

### force | propulsion:

Ion propulsion
* needs to be constantly fed a stream of electrical power to function properly.
* technology that involves ionizing a gas to propel a craft.

Reaction force
* Some reaction forces simulate gravity.
* push forces.

Rotational force
* is the most important fundamental of power.
+ Concussion: Brain
  * Rotational force is key in concussion.

Selective force
* favor the individuals of both sexes who leave behind the most offspring.
* influence behavior.

Shear force
* cause contiguous parts of a structure or liquid to slide relative to each other.
* exerts a major influence on plaque development.

Social force
* are the norms and values that characterize a culture.
* can build for years or centuries before events reach a head.
* shape math attitudes and performance.

Soviet force
* occupy Kabul, Afghanistan.
  * get the almost completely destroyed Polish city of Warsaw.
  * kill civilians in Baku, Azerbaijan.

Tectonic force
* Most tectonic forces cause events.
* Some tectonic forces have effects.

### force | thrust:

Reverse thrust
* is the opposite of forward thrust.
+ Thrust, Examples: Physics :: Force
  * Reverse thrust is the opposite of forward thrust. In this way air is pushed in the same way as the motion of the body. Reverse thrust can be used to help braking after landing. This can be done by changing the direction that a propeller turns.

### force:

Tidal force
* Most tidal forces pull particles.
* Some tidal forces cause gases.
* Tidal Forces keep ring particles from forming moons.
* affect both the Earth's crust and oceans.
* are also significantly heating the two innermost Galilean moons
  - an effect of gravity
  - differences in gravitational force
* can stretch an object into different shapes.
* cause surprising results on the solar system's largest moon.
* depend on the radius.
* heat up the planet's interior and melt the core of the long-suffering satellite.
* is the difference in the strength of ordinary gravitational force across a body.
* prevent a perfect equivalence of freefall and gravity.
* rely on gravity.
* stretch the body in the direction toward and away from the attracting object.
* tend to deform objects close to planet
  - stretch the smaller object, even though it is solid
* vary as the inverse cube of the distances between the masses.