I have a strange question and have internet-wide not found answers: An ideal pendulum hanging straight down gets a sidewards force Fh attacking at the pivot point. The whole pendulum starts accelerating along Fh. Fh: sidewarts force at the pivot point Fd: horizontal force attacking at the pendulum C/G that causes the pendulum to deflect alpha: deflection angle m: pendulum mass Fd = m*g / tan (alpha) Now, how much does the pendulum deflect? The feelings says the pendulum remains deflected as long as Fh causes a constant acceleration. But, when the pendulum is deflected from where comes the force Fd (deflection force, opposite direction of Fh)? Fd can not be equal to Fh (because that would cause the acceleration to stop). Is Fd smaller than Fh causing a slower acceleration (compared to Fh attacking directly a body with mass m)? Is there a Fd at all? If not, remains the pendulum really hanging straight down? Only a constant Fh shall be considered (no dynamic deflections because of the initial Fh step).