Blog 12: Dynamics

In the dynamics unit, there are four major topics: Equilibrium, inclines, pulleys and trains.

Equilibrium 

      In an equilibrium, the forces cancel each other out to make everything equal. In simpler terms, nothing moves when there is equilibrium.

Equlibrium problem

Inclines

     There are two kind of incline problems: Kinetic and static. In an incline, there is friction as the object slides down or as it begins to slide down.               

                                         

Incline problem



Pulleys

Assumptions:

• set your positives (+ in direction of acceleration)
• no air resistance
• T₁ = T₂
• 2 systems - 2 FBDs
• acceleration of both systems are same  

Pulleys problem part 1



Pulleys problem part 2

Trains

Assumptions:

• no air resistance
• set your positives (+ in direction of acceleration)
• no acceleration in y direction
• cords (between the cars) are weightless
• # of FBDs is equal to number of masses



Train problem part 1



Train problem part 2



You should always write the assumptions, as soon as you draw your FBDs