 Hello physics 30s. You've got a handout here talks about how to make scale diagrams and solve conservation of momentum problems But you might need some help with and you've got some practice problems So I'm going to show you here today how you can go through and solve this first practice problem using just a couple of tools, so you're going to need yourself your protractor and your ruler in The first problem in the handout we have two objects and they're going to hit and stick together We want to know their final momentum We know the mass and velocity of each of those objects as well as the angle that they strike at There's a few steps. We're going to use to go through and solve this problem First we're going to figure out the momentum of each of the objects and then we're going to draw out the momentum vectors So we're going to need a scale to do that We're going to put those momentum vectors tip to tail and then we're going to use the conservation momentum concept to solve the problem Here I go and find the momentum of each object using the mass times velocity formula I'm going to label that in the diagram. I'm going to pick a scale Here I'll divide by two in order to drive everything out in centimeters. I'm going to start by drawing three centimeters at 30 degrees So I'm going to make a reference line. I'm going to measure out 30 degrees just like I saw in the diagram I'm going to make sure that I use my ruler to make it exactly three centimeters Now we're going to use our ruler to extend that reference line and we're going to measure out another vector This second vector has to be tip to tail to the first and it's going to have a measurement of 20 degrees up from the horizontal and According to our scale it needs to be 10 centimeters long So now I have my two momentum vectors drawn out They're tip to tail and they're in the same orientation that I had in the original question Now you might have taken a look at that green vector and thought maybe there's a bit of mistake there See it looks different from the original diagram Here's what it looks like now. Wait, didn't I change that angle? But it's okay because of an idea you probably haven't thought about since the eighth grade called the interior alternate angle theorem Which basically says that if two angles kind of make this z shape on a transversal then they have to be equal And that's technically what we're using here. It takes a little bit of practice But eventually you'll start to see those angle relationships again Now that we have our two momentum components drawn out we can draw on the resultant The resultant is tip to tip and tail to tail to the two components Now I'm going to grab my ruler and protractor and measure it out I get the length of my resultant and then I'm going to get the angle of my resultant to get that angle Don't forget to put another reference line in so you have something to line your protractor up against I put a nice horizontal reference line in and then I can measure the angle And I have to make sure that I use my scale to convert that length into its original value in kilogram meters per second So here's our original question and our final answer You can see we have our green and red initial momentum components Which we've added together to give the blue resultant The reason we did this was the sum of the initial momentum on the left hand side of the drawing Has to equal the sum of the final momentum on the right hand side So we found that total using our ruler and algebra and we've shown the totals are equal We have our final answer of 24 kilogram meters per second at 9 degrees north of east