If you imagine that there is a torque due to gravity, you must imagine that there is an axis about which the torque applies. Let us choose the point where the pendulum is attached to the ground.fizzyfiz said:
The star is the axis of rotation, the thin line is the downward force from gravity, the rectangle is where the support point was moved, the pendulum arm is the bold line and the circle is the pendulum bob. You can see that the compression force of arm on bob amounts to a clockwise torque while gravity amounts to a counter-clockwise torque.fizzyfiz said:
An inverted pendulum is a physical system where a rigid body is balanced in an unstable equilibrium position, with its center of mass directly above its pivot point.
The center of mass is the point in a system where the mass is evenly distributed and the object will be balanced if supported at that point.
The force applied at the center of mass of an inverted pendulum is the gravitational force acting on the mass of the pendulum.
The force at the center of mass is what keeps the inverted pendulum balanced. If the force is not strong enough, the pendulum will fall over. If the force is too strong, the pendulum will swing too far in the opposite direction and also fall over.
The force at the center of mass can be affected by the mass of the pendulum, the length of the pendulum, and the angle at which it is balanced. Additionally, external forces such as air resistance or friction can also affect the force at the center of mass.