net force
(noun) The combination of all the forces that act on an object.
Examples of net force in the following topics:

First Condition
 If net force is zero, then net force along any direction is zero.
 That is, the net force and net torque on the object is zero in all directions.
 The first condition states that the net force acting on the object must be zero.
 Note that if net
$F$ is zero, then the net external force in any direction is zero.  There are horizontal and vertical forces, but the net external force in any direction is zero.
 force (noun) A physical quantity that denotes ability to push, pull, twist or accelerate a body which is measured in a unit dimensioned in mass distance/time (ML/T): SI: newton (N); CGS: dyne (dyn)
 torque (noun) A rotational or twisting effect of a force; (SI unit newtonmeter or Nm; imperial unit footpound or ftlb)

Constant Velocity Produces a StraightLine
 Newton's first law of motion states that if an object experiences no net force, then its velocity is constant.
 There are many cases where a particle may experience no net force.
 Or there could be two or more forces on the particle that are balanced such that the net force is zero.
 If the net force on a particle is zero, then the acceleration is necessarily zero from Newton's second law: F=ma.
 If the acceleration is zero, any velocity the particle has will be maintained indefinitely (or until such time as the net force is no longer zero).

TwoComponent Forces
 Determine the net force and the net torque for an object in equilibrium In equilibrium, the net force and torque in any particular direction equal zero.
 In equilibrium, the net force in all directions is zero.
 In each direction, the net force takes the form:
$\sum \textbf{F}=m\textbf{a}=0$ and the net torque take the form:$\sum \boldsymbol{\tau}=I\boldsymbol{\alpha}=0$ where the sum represents the vector sum of all forces and torques acting.  Newton's second law states that:
$\sum \textbf{F}=m\textbf{a}$ so objects with constant velocity also have zero net external force.  A moving car for which the net x and y force components are zero We can easily extend this rule to the yaxis.
 equilibrium (noun) The state of a body at rest or in uniform motion, the resultant of all forces on which is zero.

Forces in Two Dimensions
 Explain why force is classified as "vector quantities" Determine how to derive net force from the parallelogram rule of vector addition Forces act in a particular direction and have sizes dependent upon how strong the push or pull is.
 When two forces act on a point particle, the resulting force or the resultant (also called the net force), can be determined by following the parallelogram rule of vector addition.
 In this simple onedimensional example, without knowing the direction of the forces it is impossible to decide whether the net force is the result of adding the two force magnitudes or subtracting one from the other.
 Ideally, these diagrams are drawn with the angles and relative magnitudes of the force vectors preserved so that graphical vector addition can be done to determine the net force.
 Forces are resolved and added together to determine their magnitudes and the net force.
 freebody diagram (noun) A free body diagram, also called a force diagram, is a pictorial representation often used by physicists and engineers to analyze the forces acting on a body of interest.

The Second Law: Force and Acceleration
 The second law states that the net force is equal to the derivative, or rate of change of its linear momentum.
 These three laws state: If an object experiences no net force, its velocity will remain constant.
 The acceleration of an object is parallel and directly proportional to the net force acting on the object, is in the direction of the net force and is inversely propoertional to the mass of the object.
 The second law of motion states that the net force on an object is equal to the rate of change of its linear momentum.
 It states: the net force on an object is equal to the rate of change of its linear momentum.
 net force (noun) The combination of all the forces that act on an object.

Gravitational Attraction of Spherical Bodies: A Uniform Sphere
 Since force is a vector quantity, the vector summation of all parts of the shell contribute to the net force, and this net force is the equivalent of one force measurement taken from the sphere's midpoint, or center of mass (COM).
 The gravitational force on an object within a hollow spherical shell is zero.
 Finding the gravitational force between these massive objects requires treating them as points in space.
 Since force is a vector quantity, the vector summation of all parts of the shell contribute to the net force, and this net force is the equivalent of one force measurement taken from the sphere's midpoint, or center of mass (COM), if the object is in a uniform gravitational field.
 Once again taking the vector sum of all parts of the sphere, the net gravitational force turns out to be zero.

Translational Equilibrium
 When there is no external net force on an object, the object is said to be in equilibrium.
 In both cases – static or dynamic – net external forces and torques are zero.
 A body is said to be in mechanical equilibrium when net external force is equal to zero and net external torque is also zero.
 Since there is no net force on the object, the object does not accelerate.
 In the second type, the object has a velocity, but since there are no net forces acting on it, the velocity remains constant.
 torque (noun) A rotational or twisting effect of a force; (SI unit newtonmeter or Nm; imperial unit footpound or ftlb)

Kinetic Energy and WorkEnergy Theorem
 The work W done by the net force on a particle equals the change in the particle's kinetic energy KE:
$W=\Delta KE=\frac{1}{2} mv_f^2\frac{1}{2} mv_i^2$ .  A force does work on the block.
 The work W done by the net force on a particle equals the change in the particle's kinetic energy KE:
$W=\Delta KE=\frac{1}{2} mv_f^2\frac{1}{2} mv_i^2$ where v_{i} and v_{f} are the speeds of the particle before and after the application of force, and m is the particle's mass.  For the sake of simplicity, we will consider the case in which the resultant force F is constant in both magnitude and direction and is parallel to the velocity of the particle.
 The relationship between the net force and the acceleration is given by the equation F = ma (Newton's second law), and the particle's displacement d, can be determined from the equation:
$v_f^2 = v_i^2 + 2ad$ obtaining,$d=\frac{v_f^2v_i^2}{2a}$ The work of the net force is calculated as the product of its magnitude (F=ma) and the particle's displacement.  torque (noun) A rotational or twisting effect of a force; (SI unit newtonmeter or Nm; imperial unit footpound or ftlb)
 The work W done by the net force on a particle equals the change in the particle's kinetic energy KE:

Newton and His Laws
 Force causes an object to move.
 Objects with more mass require more force to move.
 Newton's laws of motion describe the relationship between the forces acting on a body and its motion due to those forces.
 There are three laws of motion: First law: If an object experiences no net force, then its velocity is constant: the object is either at rest (if its velocity is zero), or it moves in a straight line with constant speed (if its velocity is nonzero).
 Second law: The acceleration a of a body is parallel and directly proportional to the net force F acting on the body, is in the direction of the net force, and is inversely proportional to the mass m of the body:
$F=m\cdot a$ or$a=F/m$ For example, if you push the car with a greater force it will accelerate more.  force (noun) A force is any influence that causes an object to undergo a certain change, either concerning its movement, direction or geometrical construction.

The Third Law: Symmetry in Forces
 If an object A exerts a force on object B, object B exerts an equal and opposite force on object A.
 Newton's three laws are: If an object experiences no net force, its velocity will remain constant.
 The acceleration of an object is parallel and directly proportional to the net force acting on the object, is in the direction of the net force and is inversely proportional to the mass of the object.
 This is because the wall exerts the same force on her that she forces on it.
 This force is called thrust.
 thrust (noun) The force generated by propulsion, as in a jet engine.