 According to Newton's first law an object continues in its state of rest or uniform velocity unless acted on by an external unbalanced force. In this demonstration we're going to look at the first part of that, namely that an object continues in its state of rest unless acted on by an external unbalanced force. For the demonstration we'll use this equipment, a glass flask and a wooden hoop, and I'll begin by balancing the hoop on the flask. The object that we're going to experiment with will be the top of my ballpoint pin here, and I'm going to begin by balancing that on the hoop. Now because the pin cap is balanced on the hoop, then we know it's directly above the mouth of the flask. Now the goal is to get the cap to drop directly down into the flask, and we can do this if we use Newton's first law correctly. So you watch what I do very carefully. Now I'm going to do that again, and I'm going to do it the wrong way, and we're going to compare and see what's going on. Okay, watch again. That time the cap flipped up into the air. Now let's see what was different about those two methods. You may have noticed that the first time when I grabbed the hoop I grabbed from the inside, and the second time I grabbed from the outside. When I grabbed from the inside what happened was this. I grabbed quickly enough that the hoop deformed, and when it deformed it pulls out, and you may notice that the top and bottom of the hoop are coming down. Well what this means is that the top of the hoop will retract from the pin, and because it retracts from it immediately there's no way that the hoop can exert any force on the pin cap. As a result the hoop comes out very quickly. The pin cap simply falls straight down. Now it's acted on by an external force, the force of gravity, but that is the only thing, and so it falls straight down into the flask. There's no horizontal force on it, which would make it go one way or the other. Let's see that one more time.