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Pulley Workshop

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Sci Files segment involving students in an activity to measure the force necessary to lift a load with a pulley.

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Hi, I'm Katie in Mrs. Nowell's fourth grade class at A.B. Combs Elementary School in Raleigh, North Carolina. 00:00:00

Hi, how may I help you? 00:00:06

Hi, we heard that you were working on an experiment to learn more about pulleys. 00:00:08

That's right. We wanted to find out how pulleys work. 00:00:13

Can you tell us about your experiment? 00:00:16

Sure. First, each group was given 500 gram mass, two double pulleys, a cup, some string, and some pennies. 00:00:19

We hooked the 500 gram mass to the bottom of the pulley system that we constructed. 00:00:28

Their combined mass is called the load. 00:00:33

What did you do with the pennies? 00:00:35

We kept adding pennies to the cup until the load was lifted. 00:00:37

We then placed our cup on a balance to find the total mass that it took to lift the load. 00:00:41

Once we collected our data from two strings, we repeated with three and four strings. 00:00:46

Did each group in the class get the same data? 00:00:52

Not exactly, so we shared our data and took the class average of the total mass that it took to lift the load for each number of strings. 00:00:56

When you analyzed your data, were you able to come to any conclusions? 00:01:05

Yes. After putting the class averages up on the board, it was pretty obvious that the more strings we used, the less mass we needed to lift the load. 00:01:09

How did you calculate how much mass you needed for each string? 00:01:18

We counted the number of strings that supported the load and divided the combined mass by the string count. 00:01:22

We saw right away that there was a problem when we did our first calculation. 00:01:29

What was the problem? 00:01:33

Our mass being lifted was 545 grams when we had only one string. 00:01:35

It should have taken 545 grams to lift it. 00:01:40

Instead, it took an average of 571 grams. 00:01:44

We also found the same thing in each of our other calculations. 00:01:49

Could you have collected your data incorrectly? 00:01:53

That's what we thought at first, or that we had made an error in our arithmetic. 00:01:55

Our teacher gave us a hint. 00:01:59

We realized that there was friction in our pulley system. 00:02:01

Friction slows things down and makes it more difficult to lift. 00:02:05

That's why you needed more mass to lift the load. 00:02:09

We concluded that you can find approximately how much mass is needed to lift the load by dividing by the number of strings, 00:02:12

but you definitely have to consider friction. 00:02:19

Thanks so much for your help. 00:02:22

We won't forget about friction. 00:02:24

You're welcome, and good luck on your project! 00:02:26

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Autor/es:

NASA LaRC Office of Education

Subido por:

EducaMadrid

Licencia:

Reconocimiento - No comercial - Sin obra derivada

Visualizaciones:

404

Fecha:

28 de mayo de 2007 - 15:32

Visibilidad:

Público

Enlace Relacionado:

NASAs center for distance learning

Duración:

02′ 29″

Relación de aspecto:

4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.

Resolución: