Science Buddies: "Ask an Expert"

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So if the cassette was see through it would be something like that? Do you think you can draw a picture?

Building wise, what do you recommend would be better? I am kind of leaning towards the legos but I am not sure if there are wheels large enough and a base strong enough. I wouldn't want to go out and buy everything and have it not turn out

Are legos allowed? I would check with the teacher, they might fall into things not in the spirit of the challenge. If you don't already have them, the number of bricks you need to do a cart this sturdy might get pretty expensive.

With respect to the diagram....the pen is higher up, near the top of the cylinder. The string isn't wrapped around like you drew. Go to the beginning of the thread and look at the pully diagram Ivan added. It works like that. Weight on one side, string up into pully, down out of other side of pully to the axle. No circular loops. Just like that except the pen supports the string instead of the pully.

The only thing the string is wrapped around would be the axle.

Wow ok I think I FINALLY get it!

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From an odd angle, it would be something like this correct?
Thank you very much! I will work on it tomorrow after school and tell you how it goes!

Yes, that's right, that's the basic idea.

Making it actually work is an exercise for the student.

dang.kristie wrote:Wow ok I think I FINALLY get it!

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From an odd angle, it would be something like this correct?
Thank you very much! I will work on it tomorrow after school and tell you how it goes!

May you send me the image of your final product? Not the cart but the design. For some reason I used to see it. Now cant.

Hi(: I know it's very late to start on my project -- things have been tough and crazy so my partner and I could not have started on it any sooner than now
I'm not much of a...builder. The concept of machines just don't make sense in my head.
How would you get all the pieces to stick together? hot glue?
Would using a plastic container as the body work well?
I read all of the responses and i see the thing about the wheels being cd's and using a cork to grip.. how would the wheels be attached to the car?
Would a lever system or a pulley system be better?

All of this is starting to make me panic
Thank you so much
I know you must be tired from helping out everyone on here already

Hi shiftcomma3,

It depends what you are going to do. Hot glue sounds good for sticking pieces. Here is what I did.

I cut out 2 different pieces of straw and glued them on the front side of the cart (Right Front and Left Front). Then I got like some good strong stick (not to strong but ok)and stuck it thru the straws. Once it reaches the end cut out a necessary length. So now you should have a piece of stick through both straws. Then got 2 CDs glued them together to form a more thicker wheel. So I did that and got a bottle(Milk, Juice cap and glued it to the front of the wheels. Make sure it covers the hole of the CDs. Now what you do is poke a hole in the center of the cap. Then you insert the Wheels through the stick and make sure that the stick go through the whole of the cap. Once it is there, glue the cap to the stick. I havent gotten to the part of the pulley. I dont know about the body. You can try it but make sure its not too heavy nor too light. Good luck.

Ivan wrote:Hi shiftcomma3,

It depends what you are going to do. Hot glue sounds good for sticking pieces. Here is what I did.

I cut out 2 different pieces of straw and glued them on the front side of the cart (Right Front and Left Front). Then I got like some good strong stick (not to strong but ok)and stuck it thru the straws. Once it reaches the end cut out a necessary length. So now you should have a piece of stick through both straws. Then got 2 CDs glued them together to form a more thicker wheel. So I did that and got a bottle(Milk, Juice cap and glued it to the front of the wheels. Make sure it covers the hole of the CDs. Now what you do is poke a hole in the center of the cap. Then you insert the Wheels through the stick and make sure that the stick go through the whole of the cap. Once it is there, glue the cap to the stick. I havent gotten to the part of the pulley. I dont know about the body. You can try it but make sure its not too heavy nor too light. Good luck.

I've got the wheels done differently and it seems to work fine
i'm going to this plastic basket that i've got, which has like pattern of squared holes so it will easy to attach the wheels on
i'm not really sure about the pulley either
but from reading the other posts, i'm guessing i'll be trying out the plastic bottle thing that the others were talking about previously...
i'm working on it tonight with my partner.

my teacher, ms. sosa. is driving me nuts

What do you know? You and I have the same teacher. What period are you and whats your name?

For the pulley. I got a reel and supported it.
Anyways Good luck on your project.

i have her 3rd period
thanks
its...failing right now :[

Given her grading scheme, you're best off turning in whatever you have than not anything.

If you make a good shot at it, she gives you 60 points. This kind of thing will usually not work
the first time you build it, it takes tweaking and learning to get it really functional, and that takes
time. Which is why I recommended an early start at the beginning of this thread even if you do
not understand everything.

Hey guys. First off I want to thank you all very much for the advice and help you gave me. The cart moved about a meter and something but really close to 2 meters. But we have to get it to 2 meters for 80 pts. She marked it as a .5 and gave me and my partner 70 pts. . Anyways here is things that I have noticed today.

We were not testing in a leveled surface. When the cart stopped, the cart moved back about 5-10cm. I was questioned. So we did it again as a retrial. Still the same thing. It moved back. A bit disappointed on the results (not my partners,cart, or my fault. We did the best we could.) So it was over. I still did some testing though to see if the surface was uneven. I did it in the opposite direction. The cart did not move back. This was enough to prove that we were not on a leveled surface. So I went to another area nearby. I tested it on each direction. Guess what? Each direction had very similar results. What do you guys think?

Ivan,
All of the suggestions in this thread have been excellent and you are doing a great job trying to complete this project. I just wanted to add one little thing, and don't think it is disallowed (looking at the rules) - please ensure that the floor (i.e. the path along which your vehicle would traverse) is "polished", i.e. try to see that it offers as minimal a resistance to the movement of the vehicle as possible, since every cm counts. If the actual demo is to be conducted on a rough surface, please ensure that it is free from "debris" to the maximum extent possible.

Hi vishwa,
If I can take this experiment on the different leveled area, I would. But I have no control of where the experiment is held at. My teacher told us to do the experiment on the unleveled surface. I dont think she knew about it though. In another way, I think she does.

If it's any consolation to you when I did a project like this roughly 20 years ago, after a week of testing when it came time to actually run the test I was nervous and wound it up a little extra...which caused it to go too far (we had to stop in a specific area). Then the wheels spun as it went of the table and I lost the calibration on the retry, doing even worse. I still got a half decent grade but like you missed out on the best score due to operator error. At least you have a better reason! (the environment not being what you expected)

The important thing is that you built imagined something and built it and it basically worked. Perhaps not as well as you hoped but you did the hard part. Given more time to refine and test the design you likely would have done better.

A big part of the lesson in this kind of task is that nothing ever works exactly like you imagined it would, and deadlines often come before there is time to work out the best approach. This is a lot like real life engineering, and the best you can do is to try to gauge the risks at the beginning and plan accordingly.

I'm glad you built the thing, and that it moved. That's a big accomplishment by itself. Don't get too hung up on the exact score you got - you probably learned more about real world problem solving in this project than you're likely to learn the rest of the year in school.