Ex.
Centripetal Force Example
The string must provide the necessary centripetal force to move the ball in a circle. If the string breaks, the ball will move off in a straight line. The straight line motion in the absence of the constraining force is an example of Newton's first law. The example here presumes that no other net forces are acting, such as horizontal motion on a frictionless surface. The vertical circle is more involved.
II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.
Ex.
III. For every action there is an equal and opposite reaction.
Ex.
Newton's Third Law Example
Newton's third law can be illustrated by identifying the pairs of forces which are involved in supporting the blocks on the spring scale.
Presuming that the blocks are supported and at equilibrium, then the net force on the system is zero. All the forces occur in Newton's third law pairs.
