secondary 3 physics Newton's Law of Motion

what is force

a push or a pull on an object that results from the interaction between 2 (or more) objects

what is action-reaction of forces

force acting on each subject is equal in magnitude but opposite in direction to one another

why does force only exist as a result of an interaction

-when two objects are interacting, they exert a force on each other. 

-when two objects stop interacting, they no longer experience the force.

how can the resultant of 2 or more forces acting on an object be determined

by vector addition
When two or more forces act on an object, the overall effect on the object is equivalent to a single (resultant) force acting on it.

-The resultant force can be obtained by vector addition.

what happens when the forces acting on an object are balanced

there’ll be no change in the object’s initial velocity.