http://www.ck12.org Chapter 8. Angular Motion and Statics
FIGURE 8.8
As we can see inFigure8.8, forces−FandFwill cause the meter stick to rotate with an increasingly angular
velocity since both forces now act to turn the meter stick in the same counterclockwise direction. The meter stick
has a net torque working on it equal toτ= 2 rFsin 90◦= 2 rF.
It should be noted that just as an object in translational equilibrium can be at rest or moving with constant transla-
tional velocity, so too an object in rotational equilibrium can be at rest or rotating with constant angular velocity.
Here, though, we will concern ourselves only with the special case of static equilibrium.
Two conditions of equilibrium must be imposed to ensure than an object remains in static equilibrium. Not only
must the sum of all the forces acting upon the object be zero, but the sum of all the torques acting upon the object
must also be zero. That is, both static translational and static rotational equilibrium conditions must be satisfied.
Condition 1:∑Fx= 0 ,∑Fy=0, translational equilibrium
Condition 2:∑τ=0, rotational equilibrium