US Lesson 3 Science Video Clips
Source / In Point / Initial utterance / Outpoint / Final utterance3. TIMSS Science Public Release Lesson U.S. 3 (2:47) / 19:36 / Okay, everyone should have the “Pulley Potpourri” sheet out in front of you; the lab sheet.
/ 22:23 / While they're doing that, the person applying the effort to the simple machine, the person pulling on the string, is gonna be measuring how far they have moved the string to raise the weight ten centimeters
4. DITTO / 30:15 / I'm confused / 32:44 / Oh. Okay.
5. DITTO (5:00) / 41:51 / //(inaudible) and it's 38 centimeters. Where do you put it? I forgot. / 46:54 / So everything hung back neatly where it belongs.
Transcript
Segment 3
00:19:36 T Okay. Everyone should have the "Pulley Potpourri" sheet out in front of you; the lab sheet.
00:19:41 SN Who thought of that name?
00:19:43 T I did. It's my lab.
00:20:11 T Shh. We're gonna get started on the lab today.
00:20:18 T Shh. Folks, I need your attention up here, please.
00:20:23 T I'm glad you guys are having so much fun coloring inside the letters, but (if) I could get your attention up here, I would really appreciate it.
00:20:34 T We went over this yesterday. I'm just gonna recap it today because it's been 24 hours, and I know you forgot.
00:20:43 T You're just gathering three pieces of data from each pulley setup.
00:20:48 T You're
gathering the effort distance, the effort force and the resistance force.
00:20:55 T As I went over yesterday, you measure the resistance force just by picking the weight up with the scale,
00:21:05 T and you measure the effort distance by using the ruler in centimeters to measure how far you pull the string
00:21:15 T when you lift the weight by 10 centimeters.
00:21:18 T The resistance distance in every case is 10 centimeters.
00:21:23 T If I can have your attention back here-
00:21:28 T just quickly go over this for the first setup again.
00:21:31 T There are two rulers back at the station.
00:21:39 T You'll be using both of them at the same time.
00:21:42 T One person is gonna be measuring resistance distance; one person is gonna be measuring effort distance.
00:21:48 T So you'll have one person using the centimeter side of the ruler. There's an inches side.
00:21:55 T Don't use the inches; use the centimeters. They're gonna be measuring how high the bottom of the weight goes up.
00:22:02 T When it's at 10 centimeters, that's as far as you're going.
00:22:06 T While they're doing that, the person applying the effort to the simple machine, the person pulling on the string,
00:22:15 T is gonna be measuring how far they have moved the string to raise the weight ten centimeters. Now, some people in earlier classes were just writing down the numbers on here. They would just- be holding them here and go, "Oh, that's 55." That's not how it works. It's how far it moves. So when the person is reading the resistance and they say, "Oh, that's 10 centimeters," on this thing, then you'll stop. Where did you start? Where did you end? If you started at 55 and went to 60 or went to 45, depending on how you turned, how far would that be? Say, you started at 55, and you pulled the string down to 60 on the ruler. How far would that be?
00:23:00 SS Five.
00:23:01 T It would be five centimeters. Say, you started at 55, and it went to 45. How far would that be?
00:23:07 SN Ten centimeters.
00:23:08 T It would be 10 centimeters. So it's how far you exert the force.
00:23:14 T Audrey. It's the distance over which you apply the effort. That's what effort distance is. So if you start here and extend it that far, that's the effort distance. A couple things to be aware of when you're doing your measurements. If you pull it at an angle, your measurements won't be very accurate. so you want to make sure that you're pulling straight down in the direction that you are measuring. Secondly, you want to make sure that, uh, when you're measuring the force you're also pulling straight down. Straight down really helps on this lab. All right. So that's effort distance. Probably one of the harder things to measure in the lab. We went over- we went over resistance distance. What is it for every experiment that we're doing?
00:24:02 SN Newtons.
00:24:04 T That's force, as in Newtons. But what's the resistance distance? Look on your lab. It's already filled out.
00:24:10 SN Ten-
00:24:11 SS Ten centimeters.
00:24:12 T It's 10 centimeters. So 10 centimeters is how far we're lifting the weight up. How far we pull this to lift the weight 10 centimeters is our effort distance. The forces- I went over those yesterday. Got to zero these things. The resistance force is just how much the resistance weighs, and as you guys just said a second ago, we are measuring it in what?
00:24:31 S Newtons.
00:24:32 T We are measuring it in Newtons. Estimate to the closest quarter Newton. For effort distance- again, I showed you that yesterday- you need to tie a loop in the string, you need to zero it out upside down, you're gonna pull, and it works again much better if you pull upside down. If you pull upside down- I'm sorry. Not pull upside down. Pull straight down. If you pull straight down, you'll get much more accurate measurements. If you do it off to the side, it just, uh- it's not gonna be as accurate, and again estimate to the closest quarter. Those are the only three things you're doing for each pulley setup. There's four pulley setups. You're not gonna get them all done today. You might not even get the first one done today. That's okay. It's better that you get accurate data than that you just rush through all of these. We got time. We're gonna spend a number of days on this. Mechanical advantage, lastly. When we've got all your data, we're gonna go back and do mechanical advantage, but you gotta- have to have good data so don't worry about mechanical advantage yet.
All right. At this time I'm gonna divide you up into 10 groups and send you to a station. Get started on- well, you can do any of the pulley setups you want. It doesn't matter whether you start with the first one or not, but let me sort of divide you guys up here. That'll actually work out just, uh, fine. Cindy, I'm gonna go ahead and, uh, put you and Matt with Miguel, and you guys will be at the first station over there. Don't kill each other. Um, Diane, you guys are gonna be here on the other side of this first station. Cassandra, you guys will be on this side of the first station. Carly, you guys will be across from Matt's group. Audrey, you guys will be at this third station over here. Rupert? Yes You guys will be just across from that. Sheila and Eleanor, you guys will be where Cindy is, working at that station. And, Josh and Muriel, you'll be just across from that. And- let's see- Andrew and Zeb, you guys will be at this station back here, and you guys will be at the very last station on the end. Okay. Let's head to our stations. Take your data table. Let's get them set up and get to work.
00:26:42 SN How much are these worth?
00:26:44 T I think those were worth 50, but- T is there anything over 50?
00:26:52 S I don't know.
00:26:55 T I think it was just 50, so-
00:26:58 S Okay.
00:26:59 T Go ahead and put 50 on there. There are knots in your string other than the one at the end. You're gonna want to get those out. They don't go over the pulley well. 00:27:22 SN Are we right here?
00:27:23 T Yep.
00:27:24 S All right.
00:27:32 T You guys are sort of working at different ends here, okay?
00:27:36 SN Like this?
00:27:37 T You probably want to put the loop through. It doesn't- it doesn't really matter. 00:27:41 S Oh.
00:27:42 T But the loop hooks onto the weight. It's just you have to pull a lot more string through if you put the- better bring the string through first.
00:27:51 SN You can't just go like this and then-
00:27:53 T Sure. You can. That's fine.
00:27:54 SN Put that weight up. (You can ask me more, like, gently.) Right here. Where's the weight? This hooks around it?
00:28:05 T Yeah. This hooks through.
00:28:07 S (inaudible)
00:28:09 S //It falls off.
00:28:10 SN //You got to keep the string on the pulley though. Mr. Melville?
00:28:13 T Yes?
00:28:17 S Do you want us to do something with 41- the 41 part?
00:28:22 T I have no idea what you are talking about.
00:28:25 S How do we do effort force?
00:28:27 T You tie a loop in the string and pull down when you're lifting the weight up. 00:28:30 S Okay.
00:28:31 T And see what reading you get.
00:28:32 S Okay. 00:28:34 SN What do you want?
00:28:39 T How did you get effort distance on there, Zeb?
00:28:42 SN (This side)?
00:28:43 T You just- yeah. You need the difference. So what's the difference between 57 and 41?
00:28:53 SN We need, uh- where is the ruler? That thing-
00:28:56 SN Stop.
00:28:57 SN Oh. Where-?
00:28:59 SN (inaudible) this thing, that we went to yesterday-
00:29:02 SN Okay.
00:29:03 SN 'Cause that's what they said to us. They said that-
00:29:04 SN (shall I) measure it?
00:29:06 T She has to measure how far hers went while you're measuring that.
00:29:14 SN Actually, the up-
00:29:18 T Sheila, you're measuring how far your hand moved while she lifted that. You want to- you want to start with it on the ground and start at something even, and when she says: T "Oh, that's 10 centimeters," then you look at how far you went.
00:29:36 S All right.
00:29:37 T Okay?
00:29:38 SN Oh. Is that effort distance?
00:29:39 T So you start- it's how far the effort string goes. Yeah, that's effort distance. 00:29:42 SN Mr. Melville?
00:29:43 T Yes?
00:29:44 S What is it if it is from 50 to the one right here? Do we count one, two, three, or these little ones?
00:29:48 T Well, the little ones are what? The big ones are centimeters. What are the little ones?
00:29:54 S Millimeters.
00:29:55 T Okay. They are millimeters, or tenths of a centimeter. So it would be- it would be point something. You are trying to measure accurately, yeah. To the tenth would be fine.
Segment 4
00:30:13 SN You're gonna flip it.
00:30:15 SN I'm confused.
00:30:17 T Which one?
00:30:18 SN All right. Put your hand up there somewhere.
00:30:20 SN What are we supposed to do? Just pull up and be like: "Woo, look how far it went?"
00:30:23 T Yeah. That's it.
00:30:25 S No, seriously-
00:30:26 T You're supposed to actually measure some stuff along the way, and what would that be?
00:30:29 SN //Then what do we do after that?
00:30:30 SN //Wait up. Dude, just leave it this.
00:30:32 T What's that?
00:30:33 S Hold it, Audrey.
00:30:34 SN All we do is pull it up? That's it?
00:30:36 SN Oh.
00:30:38 SN Hold it.
00:30:39 T And how far are you supposed to //lift it?
00:30:40 SN //Hold it. That girl-
00:30:41 SN Ten centimeters.
00:30:42 T Okay. So when that's being lifted 10 centimeters, you want to know how far //you had to pull this down.
00:30:45 SN //That's what I'm saying. Hold it.
00:30:48 T Which means you need to-
00:30:49 SN Where do you start from?
00:30:50 T you need to measure. You can start from anywhere you want because it matters where you go to.
00:30:55 SN Sixty.
00:30:56 T So I'd start at something even.
00:30:57 S Sixty.
00:30:58 T But it has to be straight down, and you have to know where you started. Audrey. Audrey, it's gonna fall.
00:31:03 SN Start at 60.
00:31:04 SN All right. Hold it from up here.
00:31:05 T But you got to hold it somewhere so that you can pull.
00:31:08 SN Okay. Ready?
00:31:10 SN Oh, my god. You're //supposed to hold this right here.
00:31:12 T //You got to measure- measure it while you do it, Audrey.
00:31:15 SN You do it.
00:31:16 SN (inaudible)
00:31:17 T Yes.
00:31:18 S How do we (inaudible)-
00:31:19 SN It's so frustrating working with a blonde.
00:31:20 T Don't worry about that yet. We're gonna do that together once we got our data.
00:31:24 T Audrey, just measure while you pull down.
00:31:26 SN I don't understand it.
00:31:27 T Come here.
00:31:28 SN You have to write on this page, okay? Just this page.
00:31:30 SN Okay.
00:31:31 SN I wrote there.
00:31:34 T Audrey, let's say you started there, and by the time that thing was 10 centimeters off the ground you were here. How far did it move?
00:31:44 SN I know how-
00:31:45 T //How far did it move?
00:31:46 S //I understand it.
00:31:47 T I started at 50, I went down to 44. How far did it move? Or you can do it this way if you like that better.
00:31:54 S Yeah. Just take my pen.
00:31:55 T Started at 50, and I went to //64.
00:31:56 S //I don't mind.
00:31:57 T How far did it go?
00:31:58 SN Ask him.
00:31:59 SN Ten. Twelve.
00:32:00 T Fifty to 64 is ten?
00:32:01 S Fourteen.
00:32:02 T Okay. So it would have been 14 centimeters, right? That's all you're doing. But you're-
00:32:06 S But then where do you write it down?
00:32:07 SN I know.
00:32:08 T Under "effort distance."
00:32:09 S Okay. We need your help.
00:32:11 T But guys, I wasn't doing it for you. It was just an example of how to read it.
00:32:14 SN That's what I'm saying-
00:32:15 T Okay-?
00:32:16 S I don't know how-