Mechanics: Forces and Newton

1
Mechanics Forces and Newtons Laws

• Ch 4 and Ch 5 in the text..

2
Mechanics

• Ch4
• Identifying forces types of forces
• Forces exist in pairs
• Contact forces push, pull, tension, Normal,
  Friction, Drag (resistant force of fluid) ,
  thrust (like a jet engine)
• Non-contact forces gravity, magnetic, electric

3
Mechanics

• Identifying forces and Free Body Diagrams
• Draw all forces acting ON the object
• To aid with this, draw a circle around the object
  and look at all the forces where the environment
  touches the system.
• Dont forget the long range or non-contact
  forces.
• FBDs typically show the object as a dot and the
  forces are arrows pointing away from the dot.

4
Mechanics

• Ch 5 Newtons 2nd Law and motion along a line
• Static equilibrium. Fnet 0 in both directions
• Dynamic problems (w/ acceleration) then a
  Fnet/m, (this is required for all directions with
  acceleration)

5
Mechanics

• Friction
• Kinetic Friction Ff uk Fn (when an object is
  sliding this is an equals sign.
• Static Friction Ff us Fn (this is an equals
  sign right when the object is about to break
  free)
• In general, usgtuk where u coefficient of
  friction which is a property of the materials
  involved.