Solving Newton's Problems

Newton's laws of motion are as such:

1. Law of Inertia- all objects will remain in a state of rest or continue to move with a constant velocity unless acted upon by an unbalanced force.

2. The acceleration of an object depends inversely on its mass and directly on the unbalanced force applied to it (F=ma)

3. Every action has an equal and opposite reaction.

There are four types of problems that incorporate Newton's second law in its solution: Equilibrium, Inclines, Pulleys, and Trains. In order to solve such questions, some assumptions must be made about the conditions surrounding it. The assumptions for each type of question are listed below:


Equilibrium:
-no friction or air resistance
- a=o (y and x)


Inclines (static)
- no air resistance
-a=o (y and x)
-Fn is perpendicular to surface
-+ve axes is direction of a
-μ= tanθ


Inclines (kinetic)
- no air resistance
-a=o (y)
-Fn is perpendicular to surface
-+ve axes in direction of a


Pulleys 
-no friction or air resistance
-+ve axes in direction of a
-a of the system is the same
-2 FBDs 
-T1= T2


Trains
-No air resistance
-a=0 (y)
-a is constant
-+ve axes in direction of a 
-1 FBD to find a
-3 FBDs to find T1 or T2




After listin assumptions, draw the appropriate free body diagrams. Next use the formula F=ma and split the data from the FBDs into x and y components. Sub in values accordingly to find the desired variable.