Science Buddies: "Ask an Expert"

hi everyone,

For my physics class, I have to build a device that would be able to transport a 1 kilogram mass for a particular distance using the energy that is released from the 1 kilogram mass when it falls a distance of 10 centimeters. Here's the instructions:

http://xf5.xanga.com/78bb81227913054235 ... 345188.jpg

I don't know how to start this. Anyone have any suggestions? Thanks.

ahmee wrote:hi everyone,

For my physics class, I have to build a device that would be able to transport a 1 kilogram mass for a particular distance using the energy that is released from the 1 kilogram mass when it falls a distance of 10 centimeters. Here's the instructions:

http://xf5.xanga.com/78bb81227913054235 ... 345188.jpg

I don't know how to start this. Anyone have any suggestions? Thanks.

Hi, ahmee!

The fundamentals you need to consider for this project are how to capture the energy of the weight as it drops and then transferring that energy to somehow move the carrier. The instructions you posted talk about wheels and so on, so it seems like you need to construct some kind of car that gets it's power from the falling weight and transfers that energy to the wheels that push the car. Since the weight will drop 10 centimeters and the carrier is expected to travel 10 meters, you need to consider how to convert the energy in an efficient way.

For example, you could rig a simple string mechanism that connects to the weight, loops over a pulley or roller and then winds around the axle of a wheel on the car. As the weight falls, it makes the wheel turn and drives the carrier. The complication that you need to think about is how to sort of "mulitply" the 10 centimeter drop to get the carrier to move 10 meters.

I hope this discussion helps you get started.

Best regards!

Hi OneBriiguy!

Thanks for the information and suggestion! =)

Do you, or anyone else, have any ideas on how to minimize friction?

Thanks!

ahmee wrote:Hi OneBriiguy!

Thanks for the information and suggestion! =)

Do you, or anyone else, have any ideas on how to minimize friction?

Thanks!

Hi, ahmee!

Could you be more specific? Where do you want to minimize friction?

Hi OneBriiguy!

Is it possible to minimize the friction around the pulley and the axle of the wheel?

ahmee wrote:Hi OneBriiguy!

Is it possible to minimize the friction around the pulley and the axle of the wheel?

Hi, ahmee!

To reduce friction between an axle and a wheel mounted on it can be done in several ways. The two simplest are ball bearings and lubricants.

For ball bearings, the easiest to use is something called a "roller bearing" which has the balls captured between two concentric rings. The axle goes through the inner ring and the wheel is mounted on the outer. Try a Google search on "roller bearing" and see what you get. By the way, these may be expensive.

Lubricants are much easier, but may not work as well. One of the best ways to ensure that a lubricant will work best is to make sure the axle is very, very smooth. If you can polish a surface until it's as shiny as a mirror, then it works best. For the lubricant itself, car wax, petroleum jelly, WD-40, or simple sewing machine type oil will suffice. You probably want to avoid heavier lubricants, like car oil or grease, simply because they are messier.

I hope this helps!

Hi OneBriiguy!

Thank you very much for the information.

Now, I have another question. For the wheels, I've been thinking of using CDs or wheels from a toy car. Are there other kinds of wheels that I can use? Or are there materials I can use to make the wheels?

ahmee wrote:Hi OneBriiguy!

Thank you very much for the information.

Now, I have another question. For the wheels, I've been thinking of using CDs or wheels from a toy car. Are there other kinds of wheels that I can use? Or are there materials I can use to make the wheels?

Hi, ahmee!

You are definitely coming up with good ideas on your own. Either of those choices would be good. The CD's woudl also make it look kind of cool! (One concern I have about the CD's, though, is that they are very thin and hard. They may tend to spin on a hard floor. Wider toy wheels, although not as cool, might function better. The best thing for you to do is experiment!)

Hi OneBriiguy!

Thanks for all your help!! I tested mine a few days ago and it went 8.4 meters. =D And I got enough points to get an A in AP Physics. =) Once again, thanks!! =)

ahmee wrote:Hi OneBriiguy!

Thanks for all your help!! I tested mine a few days ago and it went 8.4 meters. =D And I got enough points to get an A in AP Physics. =) Once again, thanks!! =)

Hi Onebriiguy, since you alreaday done it ? can you tell me how , what specific materials do I need to use and how the car 's structure should look?
I really need your help

chickentown wrote: Hi Onebriiguy, since you alreaday done it ? can you tell me how , what specific materials do I need to use and how the car 's structure should look?
I really need your help

Hello, chickentown!

I did not do the project. ahmee did all the work. All I did was provide the advice that you see in the rest of this thread.

If you have questions of your own after reading through this material, please let us know. We'd be happy to help you build a successful project!

Hi one brightguy

I just realized that all the car's parts including the 1 kg mass must stay together during the entire trip and I think it would run on a cement floor
( actually on a stage ) , I've thinking to use the pulley to transfer the energy from 1 kg mass as the energy for the car to run.
I think I'm gonna build a pulley in the middle of the car, because when the 1 kg mass drop it needs to be on the car . But the problem is what should I use to make this pulley and how am i gonna attacht it to the car??? I am still unsure about that.
And for the wheels , I'm gonna use CDs too but as for the car body what do you think I should use? ( plywood rectangle base of plastic base ) And if I am going to use the wood for the body, I need to make holes in orders for the axles connect to the wheel , right? And What can I use to make those holes, I have no ideas...
So, If you could think of something , it'll be very nice of you to help me
Thanks for all your suggestions ..
Following is the intructions if you'd like to know
Joule Mobile Mass Transporter

The Objective is to build a device which will transport a 1 Kg mass a distance of 10.0 meters over a level surface (as level as possible) using the energy released as the 1 Kg mass falls a distance of exactly 0.100 meters.

Rules:

1. A 1 Kg mass cyclinder (you will be provided with the dimensions in class) with a hook on top will be supplied for use in the competition. The mass must be carried (not rolled or dragged across the floor) by the transporter.

2. The energy to run the transporter is to be stored by lifting the mass, vertically, 10.0 cm above the place (which must be parallel to the floor) where it will rest on the transporter at the end of the run. The mass can not move or rest on a slant with relation to the floor. The force of the falling mass will propel the transporter. Since the falling mass is to supply no more than one joule of energy to the transporter, care should be taken to see that its center of mass does not fall greater than 10.0 cm and that it does not swing during the movement of the transporter.

3. All parts of the transporter, including the falling mass, must move with the transporter and cross the finish line.

4. The transporter must stop on its own using only the friction provided by the wheels and the floor surface. There will be no braking mechanism.

5. After the transporter begins to move, it must be self guided. If it does not move in a straight line, the component of its motion in the designated direction will be measured as the official distance covered. If a part falls off the transporter, then the component in the designated direction to that part will be measured.

6. If a rule clarification seems to be required, it should be discussed with your teacher before the due date. "Cute" solutions which meet the letter of the rules but which violate the spirit of the contest will usually be judged unsatisfactory.

Grading:

120 points
40 points will be determined by workmanship/ design
80 points will be determined by its performance or functionality

Hi chickentown,

Your project is very similar to mine. Well for mine, I used CDs for the wheels and wood for the body. For the pulley part, I used had a piece of wood sticking out from the middle and then I attached an object (i'm not sure what it's called) on top. The object is sort of like a reel.

"A reel is an object around which lengths of another material (usually long and flexible) are wound for storage. Generally a reel has a cylindrical core and walls on the sides to retain the material wound around the core."

-from http://en.wikipedia.org/wiki/Reel

I used a reel because the 1 kg mass was attached to a string so I wound the string around the reel. So when I let go of my car, the string would unwind and the car would move forward.

Hope this helps! =)

Hi, chickentown!

Thank for pitching in, ahmee!

As for the choice of materials, I suggest that you use whatever is convenient for you. You mentioned the possibility of making the car body out of wood or plastic. I think the choice is based on what materials you have available. Making the holes required is probably best done with a drill. Wood has the advantage of being "soft" compared to the plastic making it easier to drill and shape according to your needs. But plastic would offer less friction.

Since the requirements are for the 1 kg weight to fall EXACTLY 0.1 meters, you know you must build your car tall enough to allow for this. You can decide for yourself how to accomplish this, but the first thing that comes to my mind is an "A frame" design where the weight is initially suspended from the top of an upper-case A-shaped support. Or the frame could be a rectangle. It has to be large enough to allow the weight to fall the required distance and also to have enough clearance for the pulley or reel that you use to transfer the energy from the falling weight to the wheels.

Best wishes on your project!

hi oneibrightguy and ahhmee, thanks a lot for all your helps. I figured out what I am gonna use for the car already, but I do have one more question
for the string, what type of string did you use and where can you buy it?? cause I kind of unsure which type should I use for strings. And as ahhmee said sticking out a piece of wood in the middle of the car for the pulley stand, I get that part but how do you actually attacht the stand to in the middle of the car ( make holes ?? )
Anyway, thanks all for your helps, I really appreciated....

Hi chickentown,

For the string, I just used regular string that my teacher gave me. And I attached the stick of wood in the middle by drilling a nail from the bottom of the car and up into the wood. You could also use superglue. =)

thank you ahhmee, this helps a lot And sorry for asking too many questions but just one little thing, what was your the car body 's dimension( I think about 15*25cm, is it good or it 's a little big ).

what I mean is the dimension of the piece of wood you used for the body car...

Hi chickentown,

I'm sorry. I don't know the exact dimensions of mine, but I'm going to say the dimensions were like a regular hardcover book.

hi ahhmee, the hardbook cover, is it a little too big cause I think the less heavy the faster the car would go, is it right. I've thinking I would use a 15-27 cm dimension, what do you think ??? Is it okay..
By the way thanks for your help

Sorry to bother you , but for the axles... What did you use ? Some of my friends said that they could it be sleeve tube? How do you make it fit with the CDs holes ( buy the exactly size with the holes??? or use some other thing to make it tight.. ?? )This probably the last concern I have, thanks for your patient..

Hi chickentown,

Yes, the car would go faster if it is less heavy. So basically, try to make your car as light as possible, but heavy enough so that it's steady; it won't topple when you put the 1 kg weight on it. I think your dimensions are ok.

For the axles, I'm not sure what I used because my dad helped me on this part. But, you can use a round stick that's about the same size as the hole in the CD and glue it together. And I think you can also use sleeve tubes that are maybe a bit smaller the size of the CD holes because you need to be able to fit the tube through the hole. If it's the exact size, then you wouldn't be able to put it through the hole.

Good luck! =)

As far as string goes, you want something that is strong enough and is in scale with the size of your vehicle and that will withstand any wear it will get during your experiments.

Since you are dealing with 1Kg (2.2 pounds), something like a 12 to 15 pound test fishing line might work.

A lumber yard might give you a short piece of twine they provide to customers to tie down materials they sell if you want something larger in diameter.

Part of experimenting is scrounging things that will work that are available at little or no cost.

Things like plywood used from model shops would provide a strong, very lightweight car body. Very thin, very strong, and pretty aerodynamic.

You don't want the weight to destroy the car when it lands hard, so a little foam where the weight would hit could be helpful as well. I think a light, strong car would serve you well.

ahhmee, thanks for your help, my car is looking pretty good now, but I am still unsure about the height of two stick of wood in the middle of the body car ( pulley stand )-- how high they need to be if the 1 kg mass has the height of 7cm ??? In addition to the 10 cm height drop and the string length to hold the mass, so do you think 25 cm height is appropriate for the two wood sticks???
Once more, thanks all for your helps

Hi chickentown,

The height of the stick of wood should be .100 meters - the height that you are going to drop the weight.

hi ahhmee, for the string of the pulley; we have to tie it to the axles right?

Hi chickentown,

Yes. You have to tie it or attach the string somehow to the axles in order for the car to move when you drop the weight.

hi ahhmee, I tested my car, it woudn't move , I don't know why?? Is that right that you put the axles under the body car right??? It 's not moving but when I lift the back up a little bit then the wheels start to move. But it is not moving when the wheels on the ground??? Would it because my axles are too low ??? cause under the body I put a piece of wood that have holes then stick the axles through the holes... ?? Is it right??? Oh my god the due day is tomorrow, I don't know what to do...

I think I figured out why, I think it because the axles are too low, because I did not the piece of wood with holes aside the body wood but under it.. But I don't think I have time to fix. Ok well, tomorrow only the predue day which it have to run 2 m in order to have 20 points, so i'll just take 10 points then fix it on the weekend.... Tomorrow I have a bigg Benchmark for Precal so I need to study