Understanding the Energy Transfer in a Simple Pendulum System

[n3w ton]

Homework Statement

Textbook question: We know that the pendulum will eventually stop swinging. Explain what happens to the mechanical energy of the pendulum system.

Homework Equations

None needed.

The Attempt at a Solution

I know that when the pendulum is first released from rest all its energy is equal to gravtational potential energy and at the bottom of the pendulum (at lowest point) it has its max speed and all its energy has now been transferred into kinetic energy (E_T = E_K).
In an ideal world this pattern would continue to keep going and never stop. But why does this pendulum actually stop?
My guess: something to do with gravity, air resistance, and friction on the string. Though I can't put it all together to get a GOOD answer.

Please help. Thank you Very much!

 

[rock.freak667]

In an ideal world this pattern would continue to keep going and never stop. But why does this pendulum actually stop?
My guess: something to do with gravity, air resistance, and friction on the string. Though I can't put it all together to get a GOOD answer.[/b]

You described the ideal situation correctly. Gravity has no effect on it stopping, but friction and air-resistance do. Air-resistance may be small but it is present. Friction between the pivot point and the string is the main source of friction.

For this case the initial energy is converted into kinetic energy and friction.