Science Buddies: "Ask an Expert"

This is the first time I've every been on this site and I thought I just put in a question but it's not showing. I apologize if I put this in twice. This is a 4th grade science project and it is complete, except for some testing research. We have a motor operated duck with wings that spin. The kids are connecting a 9v battery to the motor to show how fast (or the power) of the wings. They are then unhooking it and connecting a 6v batter to the motor. The wings now spin slower. The experiment is showing that the 9v. battery makes the wings spin faster than the 6v. battery. We are also trying to show that size doesn't necessarily matter. The 6 v. battery is much larger looking than the small 9v. battery. The title of the project is "DOES SIZE REALLY MATTER". We are now at the point where we are putting all the research on the board. The kids want to do a graph showing the 9v. is more powerful than the 6v. I just can't figure out how to make a graph showing the speed or the power. We don't have specific numbers for the speed. Would we do a bar graph? A line graph? I think you would put the 9v. as one bar and the 6 v. as another bar and label this on the bottom of the graph. However, what do we put on the left side of the graph for the numbers (speed?). Can we use slow, medium and fast? I went on PowerPoint but it only lets me put in specific numbers. I've been online trying to find something like this project but surprisingly, I can find no projects similar. I've been on the internet for hours and I just can't find anything. Any help or suggestions would be greatly appreciated. We just need stuff to put on the board to show the results.

Hi Mallard,

Welcome to the board!

Some thoughts:

1. You can try the different types of graphs and see which one works the best.

2. It would be best if you could the number of flaps in a given time (flap-speed). Failing that, you can assign values of 1 for slow, 2 for medium, 3 for fast, and 4 for very fast.

3. One way to generate an additional data point is to use AA batteries.

Please post again if you have additional questions.

Hello and welcome to Science Buddies:

As a science fair judge, I can say that I usually HATE seeing bar graphs. They are almost always used incorrectly. However, in the this case you can justify it The reason is that you only have qualitative, not quantitative data (unless you can do as David suggests and actually get a real measure of speed, then you want a line graph).

BTW, your battery voltage may not be 9V and 6V, as batteries change their voltage as they age. If there is a way to borrow a voltmeter / multimeter to actually measure the voltage, that would be good. Also, as David suggests, you can get more data points with AA batteries. Each battery delivers about 1.5V. If you put them in series (base to top) you can add their voltages to get 1.5V, 3.0V, 4.5V, 6.0V, 7.5V .... This can give you more data points.

If you're wanting an easy way to get graphs, the best programs for that are spreadsheets, not presentation software. Microsoft's version is Excel, but a good free one is OpenOffice. HTH and post again with any more questions!

Keith

Thanks for the help. With this being our first science fair project, it's been stressful. I like the idea of using 1 - slow, 2- medium and 3 - fast speed. This is less complicated than trying to figure out the actual speed of the winds. Maybe we can do that for the 5th grade project. Thanks also for the tip on graphs and using Excel. I was up til 1:00am last night trying to figure out powerpoint so I could show my son. I finally got it but it sounds like it would have been much simpler with Excel.
One more question: Our Title is either going to be DOES SIZE REALLY MATTER or IS BIGGER REALLY BETTER. To simplify things for the kids, they measured the length of each battery and we charted that. However, I think we need to add the speed as a second simple chart. We are going to stick with the 9v. versus 6v because there is such a big difference in size of the batteries. Most kids their age would automatically think the large 6v battery would be more powerful. However, (as a new parent trying to figure out the rules to the science fair project and what goes on the board), I think we also need a Hypothesis? Is this correct? I'm a little confused about the hypothesis. What do we put as the hypothesis? I thought it was basically the same as the question?

Question - DOES SIZE REALLY MATTER

Hypothesis - ??

Research - we are fine with this

Results - we are fine with this

Conclusion - we are fine with this

Bibliography - should we put this on the board? Do we just list all of the websites we used to research our project?

Again, thanks for everyone's help.

Welcome back!

You definitely need a hypothesis, and you can find out more about it here: https://www.sciencebuddies.org/science- ... esis.shtml
The

hypothesis is an educated guess about how things work

in other words, what you expect will happen in the experiment.

The bibliography can go at the end of the research section, which you probably will put on the board.

As you've figured out, the battery size has to do with capacity, not voltage (force) output. You could extend the experiment by finding out how long the duck will run on each battery - that should correlate to size.

Keith

Well, here I go again. I thought I replied to the last post about 20 minutes ago but I don't see it. I have no idea where it went. This posting thing is all new to me too!

Anyway, in response to Kgudger, I have been on the internet for hours just trying to figure out what is all involved in a science project and what goes in it but I'm still stumped with the hypothesis. Everything I read just says put down your "educated guess". Well, the educated guess should be "by looking at both batteries, we believe the larger battery will be more powerful than the small battery". This seems too obvious to me and doesn't seem correct. Am I missing something? The whole hypothesis thing is confusing to me. We already did the testing and know the smaller battery will make the wings spin faster so does this make our hypothesis incorrect?? We are going to test how long the batteries last this week and complete that part of the project. We (the parents and kids) are meeting up after school today to start putting the board together then again Friday after school to hopefully finish up. Again, this is all new to both the parents and kids as this is the first time any of us have ever done a science project. I thought I was smart but I'm starting to question myself. I didn't have to do anything like this in school (or college for that matter). I think I'm over complicating everything. We pretty much have everything done except for a couple loose ends (one of which is the hypothesis).

Thank you for all of your help again!!

Hi Mallard:

I hope we can clear up everything, but I have to say I'm surprised by your comment

I didn't have to do anything like this in school (or college for that matter).

Ack! As a science person, that's a pretty scary concept!

With regards to the hypothesis, yup, you got it!

by looking at both batteries, we believe the larger battery will be more powerful than the small battery

And yes, you disproved your hypothesis! It happens in real science all the time - ain't it great? That's one of the beauties of the discipline - sometimes being wrong and going on from there.

In conclusion, you have the hypothesis idea down. Your conclusion will probably include something like "In conclusion, our hypothesis was wrong. The size of the battery correlates to how long a battery can drive a load. We learned that the voltage of the battery correlates to the speed of the motor! Yeah! Go science! (And scientists - we rock!)

Keith

Your choice of "load", a DC motor introduced a factor that may not produce a "fair" comparison. Voltage is a measurement of electro-motive force and not power or energy; however, motors are extremely sensitive to voltage.

DC motors typically have a no-load speed vs voltage curve. If your definition of "powerful" was simply based on "force" then a 9 volt battery IS more powerful than a 6 volt battery by definition. When you do your duration testing, I have no clue what you will find. It will depend on the cutoff voltage of the motor (voltage at which rotation stops, not this is less than the voltage required to get the motor started so if you shut down the experiment, it might not restart without a mechanical assist spinning the load). If the cuttoff is 4.8 volts or less, then expect the lantern battery to win the endurance contest by an order of magnitude. With this load and your tests are like comparing a sprinter to a marathoner and asking who is better.

An Energizer 522 9 volt battery has a published 400 mAHr rating at 100 mA or 4 hours (continuous discharge to 4.8 volts) and 600 mAHr rating at 25 mA or 24 hours.

An Energizer 1209 6 volt lantern battery has a 40 Hr rating at 100 mA for a similar cutoff voltage; however, if the current draw is only 25 mA, you can expect 250 hours (based on published curves).

In other words, you can expect to get about 6 times more energy out of a 6 V lantern battery than a 9 V transistor radio battery if your load will operate down to 4.8 volts and the current draw is 25 to 100 mA.

This is a case where the behavior of the load has a significant factor on how much usable energy a given battery is capable of providing.

Hi Keith. I love your response. We got it now. The light bulb finally went off.

I graduated in 1985 on the west coast and went to a very small public school in the middle of no where (in Oregon). I never had to do a science project but loved my science classes (even took AP science in high school). I only took the required courses in college since my degree is in Finance. Not that I don't like science (I find it very interesting and my son will most likely become some type of scientist or engineer), I'm just more interested in Finance. You've been a great help. Maybe we can chat again next year (5th grade science fair project)!!. It's been fun