Alright folks. So in this problem we have a marble and it's moving according to this potential energy function or this potential energy graph. And let's take a look at the first part here, which is we have to figure out the labeled points where the force on the marble is equal to zero. Now remember the big idea here guys is that the force is equal to zero when the potential energy graph, when you have X. Is flat. So that's the most important thing that you need to remember that there's no force when the potential energy graph is flat. So if you look at this at this graph here, this is not flat. This is not flat. There's only two points that actually are flat over here too with the labeled points which is point B and D. So that's the point in which momentarily the graph actually flattens out as it sort of curves as it changes from curving up to down. So in other words, the points in which the force is zero are going to be points B and D. Those are your two points here. Right. So it's going to be these two. All right. Now, let's take a look at the second part here. 2nd part asks us to calculate well which one of these labeled coordinates is a position of stable equilibrium. Remember we have stable and unstable equilibrium. And remember the rule you use a smiley face, if you're smiling, that means that you're stable. And if you have a sad face, that means that you are unstable. Right? So you want to be stable. right? That's that means good. So we're looking for the happy faces, right? So that means that the um it's gonna be point B. Alright, so that is point B. This is also just the one that is stable. This one is unstable, which means um that if you had a particle, when you remember one way you can think about this is if you had a little ball that was at the top of this hill, if it moved like a tiny bit to the left or right, it would fall down the hill. But if you had a ball over here at the bottom of this bowl, then it would just stay there, right. It would always just stay there unless something jostled it out of place. Alright guys, that's it for this one.
