Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Pulley Lab – Mechanical Advantage

Posted on: March 19, 2009


I’ve been doing this lab for a number of years, but it needed a make-over.  I did that today, it’s beefed up a little and I added a data sheet.  I’ve gotten away from the lab notebooks because they are just too hard for me to collect and take home, and I never seem to be able to grade at school.  I’ve headed towards more of a “min-lab” format that I read about in The Physics Teacher a year or two ago.  This has greatly cut down on my grading, which allows me to do more lab and hands-on work, which gives me more to grade.  Somewhere in there we reach equilibrium.

This lab uses two double pulleys, some mason line, a ring stand and ring,  spring scales, a meter stick and a weight.  I like to use a 1 kg weight.  It’s heavy enough that they can feel the difference when the pulley helps out, but not so heavy that everything is falling over.  I found it helpful to have two or three different size strings.  The short string for the first three configurations is about a foot long.  They then switch to a second string that is four or five feet long.  I would suggest you play with the lab and then make up the appropriate length strings.   I like the pink mason line, it’s easy to see from across the room, so I can tell what’s going on at every work station.  It’s also easy to find when things are misplaced.

Here is the lab and data sheet:

pulley-lab-rev-c2

pulley-lab-data-sheet1

MA 5 Solution

I would love suggestions and ideas to improve this lab.  I’m still not thrilled with the overall lab, but it’s the best I’ve been able to do so far.

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8 Responses to "Pulley Lab – Mechanical Advantage"

[…] Pulley Lab – Mechanical Advantage « Physics & Physical Science … […]

i think it would also work as grade 8 science lab

great work

I just completed a similar lab with a 10th grade physical science course. The combinations I had students use was a single fixed, single moveable, two pulleys pulling up, two pulleys pulling down. This could have continued to more combinations, of course.

I had only talked about work = Fxd prior to this lab, so students did not have an idea about mechanical advantage (which hopefully will be discussed and brought to the forefront after discussion tomorrow).

I am looking into making it more inquiry based. Perhaps just by asking students to determine how number of pulleys and the order of the strings affects the force needed to lift up a 500g object. The wording on this needs to be refined.

Thank you for sharing your lab. I love seeing another teacher’s approach to topics.

great lab! but my physics students were stumped trying to achieve an MA of 5 with only 2 double pulleys. Do you have a diagram of the solution?

I added it to the original post. I’ve also updated this lab and I think it works even better as a discovery lab. http://wp.me/p2NL0-js

I do a pulley lab with middle school students regularly and sometimes as an enrichment lab for upper elementary. I use full size block and tackle sets, in addition to the toy pulleys. With a bosun’s chair, the students can lift me – once they get to the set with 4:1 or sometimes it takes the 6:1 (two triple blocks). Downside: These rigging blocks are quite expensive (5″ nominal triple $100-300 ea. depending on brand & origin) and only found online or with industrial suppliers. However, big pulleys make a much more satisfying and memorable lab. My supporting paper material is much like you would expect. I also have a nice SmartBoard show for it.

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