This was a great little activity - there was some working through frustration, but we all worked as a team and learned a lot in the process. Depending on your nature collection, knot tying and finances, you may want to vary the materials...
You will need: plenty of string, a longish straights stick, somewhere to hang the stick, some items to hang (we had some birds nests we made to put things in, but you could easily use small buckets or flowerpots), a ruler.
We started with the stick. We hunted for a while to collect a stick that was as straight as we could make it. We carefully measured, the stick and found the middle. Now, we tied a piece of string around it - we wrapped the string around twice, then tied the ends together at the top (making one big hoop). We then hung the stick to make sure it balanced - this required a bit of shuffling the string to make sure the stick was in a straight line.
Next, we found something to hang - my oldest used the home made birds nests (like in the picture above) but my 4 year old tied on flowerpots as that was easier. We tied two hoops around the object (so there were 4 pieces of string coming up from the bottom, then tied them together at the top with 1 piece of string. After all this knot tying we were experts! If you are not confident at tying knots, there is a video, here, that you can follow.
Finally, we tied them onto each end of the string and, again, shuffled them about so they could hang evenly. We learned loads about balance and discussed how hard it is to make things balance during this time. My 6 year old had to walk away and have a little drink pause a few times to help manage the frustration. During this pause, we collected things we wanted to measure.
Finally, our balance scale was ready and we could weigh our things! We compared the weight of pine cones, two spades, sand and mud (in the flower pots!), leaves... anything the children could collect. They had a lovely afternoon testing their hypothesis... I hope you have as much fun!