## Jelly Baby Wave Machine

Libby has been working her way through the Physics IGCSE course from Sam Martell and got to the section about waves. There are some excellent resources (see my other article on YouTube Videos) out there but nothing quite beats building a wave machine to explore the motion of waves directly. We went to the Bradford science fair a year or so ago and saw something there that we just had to have a got at building.

It’s basically a long piece of duct tape with bamboo skewers stuck to it and jelly babies stuck to  the skewers. When you suspend the tape and wiggle one of the skewers at one end it causes a transverse wave to propagate down the line. The waves will exhibit all the expected behaviours just like any wave does it’s just in a non-conventional medium! It’s perfect for playing with waves and you can eat the jelly babies afterwards if you want. It was pointed out that you don’t need to use jelly babies and the at something more permanent could be used and that is true but it’s not as engaging as making science edible, in my opinion. So if you fancy having a go, try following these instructions and take a look at the video we made on youtube (links are all below). So onwards…

First your going to need some basic equipment:

1. A roll of duct tape long enough to do twice the length you’re planning.
2. Bamboo skewers
3. Jelly Babies (more than you think! as some get eaten)
4. 2 metal rods or thick wood dowels for anchor points at each end.
5. Tape measure
6. Clamp stands or some way of suspending it at each end.

Our pile of kit

Our pile looks like this on the right.

Start by laying out the skewers on the tape, 5cm apart. Mark the middle of each stick and make sure you line up the middle of the stick with the middle of the tape and keep them perpendicular tot he tape.

Putting the sticks onto the tape

Do it alongside a ruler and when you reach the end lay another stretch of duck tape over t he top of the skewers to keep them in place. We used a second role of tape and kept them both running continuously.

Alex and Libby kept at the layout of sticks

Cassie worked on marking the middle of the skewers. We anchored a metal bar at both ends

And when we were done the whole tape was 4.5m long. We then rolled it up to make hanging easier.

Then using a couple of lab stands clamped to the kitchen bench and table…

We loaded the jelly babies. As we did so we noticed that  not all jelly babies are the same and this caused the sticks to start to hang lower on one side than the other so we went for colour pairs, putting only the same colour sweet on the same skewer. This seemed to balance things nicely.

Once all the skewers had a jelly baby stuck on each end your done. Make sure it does not sag too much by pulling the ends out a bit.

And give it its first wiggle by moving the end of a skewer at one on up and down to start a wave. The tension and weight of the set up will only want to go so fast, so as long as you’re not brutal with it, you can send a beautiful wave down the length and reflection at the other end will send it back.

Finally we made a video of the machine in action. It’s here on youtube.

So I hope you have fun making your own and do email or leave comments letting us know how you got on.

## IGCSE Physics revision videos

I just found this set of video’s on YouTube. The channel seems to cover both Edexcel and Cambridge IGCSE physics. Libby too a loo at he waves video today and said it really helped. Often it’s a case of having something explained by someone else who inevitably does it in a different manner or uses different phrases. This chaps bio says he is a Physics Teacher at Sherborne School, Dorset, UK. Anyway, hope it helps with the revision, teaching etc.

## Halloween and Pumpkins

Well Halloween is here again and the kids want to go around the neighborhood trick or treating as usual. I seem to remember that before that we used to go around with a hollowed out turnip and knock on the doors of people we knew. Now it is pumpkins, costumes and every door that has a light on. It’s moved on and I think got a bit better, though somewhat commercialised in parts. We try to stay away from that and stick to made up costumes and hollowed out pumpkins where possible. We bought 4 small ones this year so everyone could have a go, we also got some really good sharp knives that did an excellent job of cutting through what has always surprised me as very tough skin.

Cassie started off by cutting out the top and marking up the front face then removing some of the flesh with a spoon.

Lid off and flesh removed

Then she began carving the face out with a good sharp knife. Which makes it easier. Best to have an adult do this part if your kids are too young.

Cassie carving her pumpkin

After Cassie the other kids did theirs and after much clearing up the finished four pumpkins were ready. (Sam is too small yet to have his own!)

The finished ensemble

Well the evening went very well, with kids all over the street and too many sweets being given out. The only problem that remained was what to do with the leftover pumpkin. Well this year, as always we try to use it up. It’s never easy as it’s not been favourite, but we tried a simple roast pumpkin and stock soup accompanied by a pumpkin and rosemary soda bread. It turned out to be a huge hit with everyone.

Roasting Pumpkin seeds and adding salt to flavour

Pumpkin and Rosemary soup.

Well we still have loads of leftovers to use up so I expect we’ll be trying other recipes in the very near future. I hope you enjoyed your evening.

## Geocaching handheld GPS’s

Here’s an example of some GPS units that may work for you. For a broader range check out this link: Handheld GPS It’s not an exhaustive list by any means but its a place to start. Just stick to your budget. You should be able to get something for  under £100. I spent a bit more to get the onboard maps function. The Garmin eTrex Summit:

It comes with maps installed but you will quickly realise that you need more detail. So download and install the OpenCycle map, which is freely available from http://talkytoaster.info/ukmaps.htm More information on Open maps go to Wikipedia http://en.wikipedia.org/wiki/OpenStreetMap.

And some others that may work for you:

## Alfalfa sprouting

OK, so I couldn’t resist posting this on. Using a webcam microscope attachment we took a timelapse of an alfalfa seed germinaring over night. The whole experiment took 36 hours and was shot on low magnification. Let me know what you think.

## Mushroom and onions

I thought it woud help to see the sort of image that you can capture with a reasonable priced microscope at home with basic kit. So here are a couple of photos.

## Onion Skin

First is the classic onion skin as mentioned earlier: It’s taken on a microscope-webcam set up.

Onion skin.

The webcam fits in place of the objective lens that you normally look through so you don’t get  the same picture as you can see when you loo through the scope. However it does give a good reliable and easily used set up. Resulting in a rather nice”text book image”.

## Mushroom Spores

The next shot was taken using a regular digital camera pointing down the scope through the objective lens used to view the image. This tends to give almost exactly what the observer can see if they look directly down the scope.

Mushroom spores

Both images were easy to obtain and Alex (aged 10 at the time) was able to do most of the work himself with some supervision. We spent quite some time looking at different things under the microscope and quite often get it out to examine something that one of the kids have found in the garden or on a walk etc.

If you need any suggestions or have questions leave a comment and I’ll see what I can do to answer. I’m not an expert, just a parent trying to give my kids the chance to look a things in a different way.

## Microscopes

We’ve tried a few from the basic plastic ones just to get you interested in what you can see to a little more expensive and capable of some quite reasonable reproductions of those text book photos like the “Onion Skin” slide. It’s like all things, you get what you pay for and I wish I had paid a little more in the beginning, rather then keep trying cheaper models in the hope of finding the right one. You don’t want to be spending time sorting the optics, the student’s will get restless and move off and you will have wasted time and money.

These are some scopes that look like they fit the bill from low end and mid range. I’ve also added a couple of items that are basically pre-prepared slides. These already have specimens on glass so all you have to do is up them on the microscope stage and view them. No hassle and a great way to get started.