# Simple pendulum is not so simple as it seems to be? [duplicate]

Does a simple pendulum come to stop due to the action of gravity ?

Consider : No air drag, No change in place.

• – user43617
Nov 4, 2014 at 16:04
• No. It has $EP$ at the height from which it is dropped, and this $EP$ keeps getting converted to $EK$ and then back to $EP$ at the other extreme end.
– user49111
Nov 4, 2014 at 16:04
• Is the air the only "agent" that can slow the motion of the pendulum? Nov 4, 2014 at 16:05
• Cant we state this with the fact that "horizontal velocity of an object will not get affected by gravity acting perpendicular to it" ? Nov 4, 2014 at 16:07
• @Jun-GooKwak I actually want to know will there be an effect of gravity causing any dissipation that I couldnt find there. Anyway, Thanks for conveying the message. Nov 4, 2014 at 16:13

Say you release the pendulum, then on the other side, there is a period of time where it is motionless where $E_k = 0$. In addition, this is the point where $E_{p,max}$. At the next instant, the pendulum will swing back increasing velocity due to the acceleration of gravity pulling at the weight at the end of the pendulum. Following the Law of Conservation of Energy, $E_{p,max}$ is converted into $E_k$. At the pendulum's lowest point, $E_p = 0$ and $E_{k,max}$. The pendulum begins to decelerate due to the force of gravity as it swings back up, and it will reach the same height as the opposite side in an ideal system.