What you need to know from Physics:
Force:
Generally considered as a push of a pull exerted by one body on another. Interaction occurs when there is direct contact between the bodies. Gravitational, electrical and magnetic forces do not require direct contact. Force is characterized by magnitude, direction and point of application.
Particle:
An object having mass but the size is neglected.
Rigid Body:
A combination of a large number of particles which remain in a fixed position relative to each other, both before and after the application of a force.
Newton’s Three Laws of Motion
First Law: A particle originally at rest, or moving in a straight line with constant velocity, will remain in this state provided the particle is not subjected to unbalanced forces.
Second Law: A particle acted upon by an unbalanced force F experiences an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force. If F is applied to a particle of mass m then: F = ma.
Third Law: The mutual forces of action and reaction between two particles are equal, opposite and collinear.
Newton’s Laws of Gravitational Attraction:
Where:
F = force of gravitation,
G = universal constant of gravitation m1,
m2= mass of two particles,
r = distance between two particles.
According to this law, an object's weight is defined by:
in which:
m = mass of object
m2 = mass of earth
r = distance from center of earth to particle
