All right, so welcome to lab number eight, the impulse momentum theorem. This is the experimental part, and I just have this up because it's got the title and the whole thing. Plus, they're very cool pictures. These little GIFs, do you call them GIFs or GIFs?
GIFs. GIFs, okay. So, come on over here, Tom. So the experiment... Oh, here, come back over here for a second.
This is what the setup looks like. So we've got a spring. It's going to provide the force. We've got a cart, motion sensor, flat track, so when you do the experiment... Make sure the track is nice and flat.
And then back here is a force sensor, which I forgot in the other room. So we're actually going to stop the video in a minute and then go back. But anyway, that's the setup right there.
And you need to measure the spring constant. And I know we've already done that before. So you're going to be using a very light spring, the exact same spring you used before.
Remember, they're all slightly different. And besides, you should be well practiced at finding the spring constant. All right.
So there it is right there. Remember what I recommended. Get a weight pan that's 5.0 grams, and then get 300 grams. Put the most on there that you can.
The bigger the measurement, the better. Now, you don't want to pull on the spring so hard that the spring deforms, but 300 grams won't deform the spring. Okay, so you have to make a measurement. So, like, right here I'm close to the tabletop, so I could measure the distance up to where the spring is, and you could do it to, like, a millimeter, somewhere on the spring there.
You could measure, like, the bottom of the loop right there. So, anyway, that's, like, 50 whatever, but I'm not doing this experiment. You're doing this experiment. Okay, so I got that number right there.
Oh, let me go the other way because it's actually going to get longer. So we're sitting here at like 40, 45 point something. And then we put that on there and we bring it down and down and down. Uh-oh. 200 grams.
200 grams. I think I put 300 on last time. Oh, my gosh.
Look at this. This is crazy. All right, I'm just going to put 100 on there right now.
But when you do it, make sure, like, do it off the end. end of the table so you can put more than 100 on there. Okay, but anyway, so measure that distance again.
So remember, you're measuring the bottom of the loop right there. So you can measure the bottom of the loop as best you can. That's why you want to put 300. So you get a really big measurement. So if you're just off by a little bit, it's a little bit and a huge amount. Okay, so remember, you take the weight.
So this would be 0.105 kilograms times gravity. 9.81 and then divide by the stretch Delta X. Okay, so that's that so I need to get that off of there And the other thing you have to do is measure the mass of the spring with the cart All right, and I got that right over here Remember you got to zero out the balance and then once you get it going move the riders But it's somewhere around two hundred and sixty plus between 250 and 275 Okay, so you definitely need those measures somebody in the lab group gets on that right away because it's something you can do and should be doing right away okay so we'll be right back because I have to go get a force sensor okay so welcome back to the experimental part Tom Is this adding on or is it like brand new? Adding on.
Oh, how did you deposit it? Well, it's brand new. Okay, okay.
All right. So anyway, this is the setup right here. You've got the cart and it's got a string attached to it. We use these highly technical twist ties.
And they'll hold them right on there. Carbon fiber, nothing but the best for you guys. And I can show it to you right here. So you just run a little carbon fiber.
twist tie right through that loop right there. There's the spring right there. This end over here we're not using. I usually like to just leave it open.
Sits on the track there. There's a little magnet but that won't cause any problems. And then there's a force sensor back here. The force sensor needs to be zeroed. So you can see right now it says zero right there.
So you can push collect on capstone where it says record right there. Collect. And then you can push this button and zero it. So right now on my screen, the blue line on my screen over here is force, and it is not quite on zero. So if you don't get it quite on zero, then your integral, when you go to do the integral of force over time, you might get a little bit of error.
So make sure you get your force sensor zeroed. We're going to do it again this time so you can see it. So I had to make sure everything was set up correctly.
Alright, so anyway, this is the spring. It's got a little string attached to it. It goes to the force sensor. So this will measure force over time. Now down on this end is a motion sensor.
And that's going to measure the speed of the cart as a function of time. Actually, the velocity of the cart. So when the cart approaches a motion sensor, it'll be like positive. And when it moves away, it'll be negative.
We're going to put both those traces on the same graph. So you can see right now I have red. Let me move this bubble box out of the way. So I have this red trace, which is the velocity trace.
So you see when it came in, it was supposedly going in the negative direction. And you measure how fast, the fastest it's going, and then the spring starts slowing it down. It goes slower, slower, slower, zero. and that means it's fully stretched out, and then it's going to speed it up, but in the opposite direction.
So faster, faster, faster. And all the way up in the top is the maximum speed. And the way you measure the speed off the graph to get a really good measurement, you go to this button right here.
It looks like a target. That thing right there, you click on that, and it's called a multi-coordinate tool. So right now I've got two of them open.
Let me see if I can open one more. All right, right there. Multi-coordinate tool.
So I'll open that up. Let me get these guys out of the way. I already got two of them open. But anyway, just move that over.
But you can use your arrow keys on your computer to get the very, very biggest negative value. So it's negative 1.34. And then you can zip it ahead, all the way up there to the top, and find the biggest one.
So positive 1.32. And to get the integral... You push this button right there, and that will give you the integral under the curve. But we want the force curve. We're going to put this little bubble box here because I got air, like I mentioned, and then I get the area.
So you can see the area. See how it's all colored in dark blue? And there's the area right here. Now, you know, the ciggies, when they give you ciggies, see it says area 0.4093.
When they give you the ciggies, they'll only give you like one ciggie. It's kind of a flaw in their program. So each time that somebody's got to be on their toes and make sure you get like three ciggies.
Three or four ciggies. Because you can always get rid of ciggies. You can never get them back, though, if you don't get enough. All right, so let's run one from scratch. All right, so you got this thing all set up.
What you need to get first is the distance just before the spring starts stretching. Okay, so right here, you can see if I go like there, the spring is stretching. So you go to where it's all the way stretched out, but there's no spring stretch. Alright, and then measure it. So like right here it looks like I'm about 40, 45.9 centimeters.
Then I'm going to take this thing and I'm going to push it. I'm going to push it and it's going to go out like that. And somebody's got a videotape over here to find out what the maximum stretch is.
Okay, so you're actually doing two experiments at the same time. So you're changing the force over time. And then you're going to measure the change in the momentum, and you're going to measure what's called the amplitude, how far the spring stretches.
And by the way, that's the point where the cart stops moving forward and then gets pulled back and starts moving in the opposite direction. Okay? So very, very important. You get your slow-mo video out on your iPhone, and you get down here, videotape it, and get the number.
off there. But remember, you've got to subtract it from the number where it's not stretched at all. Sound good. Sounds good. Okay, so let's go ahead and do one.
So I'm going to bring this back here. And by the way, you give it like eight to ten pushes. If you've got plenty of time, do ten measurements.
Always take ten measurements if you can. But the minimum is eight. But push for ten.
Alright, so here we go. I'm going to push collect. I'm going to zero my force sensor. And I've got my sampling rate for 50 Hz. So I'm taking 50 measurements per second.
And now I'm going to go ahead and push it. Alright, and then I can stop it. Alright, and why don't you come on over here. Let me move this out of the way so Tom can get a look at the screen. Now, you can see right now everything's squished because I got a whole lot of time where I wasn't doing anything.
So, I can move everything down like this. And I can stretch this, not quite so much. Okay, over here, this is the force over on this side. By the way, the way you get two axes is you push this little button here with the green star. And it'll let you put force on one axis and velocity on the other.
Okay, and I'm just going to stretch this out a little bit so we can see it better. Alright, and then I'm going to move it down. Alright, that looks great.
Now, you can see this time I really zeroed the force sensor just fine. So I don't need a bubble box to do it. And the button's on, so the area's here somewhere. Let's pull these things out.
So, unfortunately, I think I moved it. It's way over on the... Oh, there it is right over here.
Okay, so it says 1.1 newton seconds. So if you want to change the number of sigis, right-click on it, defer. And...
then I'm going to put three, I'll put three, three decimals. Okay, so you can see it's 1.057 newton seconds for the area, the red shaded region, and then to get the speeds, you get this tool right here the multi coordinate tool and you go down I like to get close and then just use the the arrow keys okay so that lowest value was minus 1.76 you can see that last one I really whipped it 1.76 and then up here 1.71 okay so one was negative one was positive and then when your video camera You just go ahead and look at the video and find out what the maximum stretch position was. Now, since you're actually not launching the cart with any fixed amount of force, you're just pushing it. So you need 10 different kinds of pushes. So you can have a really weak push, and then medium pushes, and then a couple really good pushes.
Now, you don't want to get too close to the motion sensor, but just get 10 really good... pushes in through here and then you'll be able to plot the data that you get. All right, that's about it. What do you think about that?
This is a cool, cool lab. All right, take care and we'll see you next week. Bye.