Chapter 8-  Rotational  Equilibrium and Rotational Dynamics

1. Torque( t )-  measure of turning effect produced by a force- unit   N.m

            t =  Fd

2. Bodies in total equilibrium- Force balance and torque balance

     S F = 0;      S F_x = 0

                         S F_y = 0

     St = 0

3. Center of gravity-   Location where the entire weight of the body can be considered acting

      x _cg  =   (w₁x₁ +w₂x₂ +.............)/(w1 + w₂ +............)

      x_cg  = ( m₁x₁ + m₂x₂ )/(m₁ +m₂)

4.  Rotational inertia  I = S mr²

     Newton's second law for rotation   S t  =  I a

    A  torque produces angular acceleration

5. Rotational work   W = t q

    Rotational Kinetics energy    KE =½ I w²

    Angular momentum                L =  I w

6. Conservation of angular momentum

    When the sum of the external torques are zero, the total angular momentum of an isolated system is constant

    I_o w_o =  I_f w_f