Static Equilibrium

1
Static Equilibrium

• Why object remain stationary

2
Static Equilibrium

• An object is in static equilibrium if
• It has zero velocity
• The net force acting on the object is zero
• The net torque acting on the object is zero
• Mathematically speaking
• V0, Fnet 0, Tnet0
• The first two conditions make sense, an object is
  not moving if the net force acting on it is zero.
  Why does the net torque need to be zero? (demo)

3
Solving Static Problems

• Draw the FBD of the body. Do not draw the body as
  a dot but instead show the relative positions of
  all the forces
• Choose an x-y coordinate system
• Resolve into components any forces that are at
  angles
• Write a net force equation for both the x and y
  direction
• Choose a pivot point
• Write a net torque equation based on the pp
• Solve the equation (max of 3)

4
Center of Mass

• If a solid object such as the board in the
  previous question has a mass..we treat it as if
  all its mass were concentrated at one point.
  (center of mass)
• Regular shaped objects center of mass
• Irregular shaped objects use calculus to find.
  We will not do this. ?