Object subjected to a linear restoring force about an equilibrium point will oscillate that equilibrium point with simple harmonic motion. Displacement of mass attached to a spring is sinusoidal ( Angular frequency does not depend on amplitude of oscillation ( (t) x cos( t. F net a = m d x2 = 2 x dt2. Torsion pendulum - disk attached to rope which is attached to a fixed point above, as the disk rotates the rope twists also. If the disk is turned an angle. , the pendulum will go about simple harmonic motion. Direction of restoring torque is whatever allows the rope to twist back to equilibrium position. Objects that are supported by a pivot that have a restoring torque provided by gravity. Weight of an object hung by a frictionless pivot exerts a torque that is proportional to the horizontal displacement of its center of mass away from the pivot. It acts to reduce the horizontal displacement.