HOW TO BUILD A MOTORBOAT THAT IS POWERED BY SURFACE TENSION

[harvey_93]

Dear sir/mam,

How will I build a motorboat? because I did'nt understand the explanation that it should have a slot at the end. And I accomplished that but when I start experimenting, the boat did'nt move at all. So please HELP ME...

[deleted-71588]

What did you put in the slot (cotton ball, sponge, something else)? What liquid did you apply to the material in the slot? What size boat did you make? How much draft (how far down in the water does it ride)?

Did you read the reference articles on surface tension and understand them? If you read them and did not understand them, you should look at one of the other surface tension experiments and look at their reference articles and see if they are easier for you to understand.

The effect of surface tension changes caused by a liquid surfactant are small so you need to be using a small boat that doesn't weigh much and doesn't have much draft. Once you start adding detergent (or other surfactant) to the water, a diffusion process starts that will soon disperse the surfactant and as this happens, the surface tension differential between the "treated" end and the "untreated" end will decrease. Once this happens, you need to start over with fresh water and you may have to rinse out your container several times to eliminate enough of the residue. The less detergent or other surfactant you use, the more experiments you can run in the same water before you have to start over and the less residue there will be to rinse out.

Hope this helps.

[harvey_93]

Thanks for your reply!
We put in the slot a sponge. We did'nt apply any liquid to the material in the slot and that is actually my problem because I don't know the model of the slot or even the boat and so the water we put in the channel is getting inside the slot.
So I want to know the model of the boat..

We use a small boat it is only 5 cm. in length and 3 cm. in width and I think more or less it is 5 grams. Ahm what do you mean by draft?

[deleted-71588]

If you look up "boating terms" or "draft" in a good dictionary and look for the nautical meaning, you should find it means how much water it takes to float the boat. In other words, how deep into the water it rides. For this project you want a light weight design so that there is less "bow resistance" so the small surface tension force differences will move the boat.

The water from your tank is supposed to wet the sponge. You just need to take the boat out of the water, squeeze the sponge to get rid of most of the water, then apply one or two drops of liquid dish washing detergent to the sponge and then set the boat back into the water.

I suspect that it should move once you add the detergent given your dimensions and weight.

[harvey_93]

I did the experiment and turned unsuccessful because when I put the boat on to the channel and start propelling after a second it will bump into the side and it will stuck there and then I will start all over again. Why is this so? please reply as soon as possible..

[deleted-71712]

Well, your propeller is creating some force and causing the boat to move in some direction -- that's progress!

It sounds like what you're trying to do is send the boat down a narrow channel, but instead of moving in a straight line, it veers off sideways. Is that correct?

The direction in which your boat moves is determined by the sum of all the forces acting on it. The propeller creates one force, but the water also pushes back against the boat.

I think you were talking about experimenting with asymmetrical boat designs, so if you chose one of those, it's possible that the water flows more smoothly over one side (left or right) of the boat than the other. As a result, the net force on the boat would have some sideways component.

On the other hand, it's also possible that your propeller is not aligned perfectly and that the force it creates is not exactly parallel to the front-to-back axis of the boat.

To troubleshoot this, it might help to put the boat in a larger body of water -- not something narrow like a channel -- and observe the ripples in the water around it and the path it takes over a longer period of time (since the wall won't be there for it to crash into).

Amanda

[harvey_93]

I think it is better but how we will measure the speed of the boat when it is put into a large body of water?
Thank for your reply mam

[deleted-71712]

The suggestion to put the boat in a larger, non-narrow body of water is for troubleshooting -- finding out what the problem is that's making it move sideways so that you can fix it and put it back in the channel to do your original experiment.

Amanda

[harvey_93]

Okay I get it but we don't have enough time to do that. Is it okay to use magnet to repel the boat thus preventing it from bumping sideways?

[deleted-71588]

Without knowing your exact hypothesis and precisely what you are measuring, I can't answer

Is it okay to use magnet to repel the boat thus preventing it from bumping sideways?

because I can't tell you if it will affect your measurements and in turn your conclusions. Placing a magnet on the boat will add an additional magnetic force in addition to changing the mass of the boat. The best guess is because it will affect the behavior it will probably affect your measurements and likely your conclusion.