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I admit that at school physics was my poorest science subject, I just didn’t understand the fundamentals having had cover teachers during critical parts of the curriculum and I struggled, that was until I started teaching the subject during my teacher training and I taught myself the fundamentals in a way that I could get it and understand and then could pass onto my students. Newton’s laws are of course one of the fundamental aspects of physics and the Newton’s Cradle shows some of the laws perfectly.
Newton’s Cradle is set up in such a way to show the laws of conservation of energy, conservation of momentum and friction. In the traditional Newton’s Cradle steel or titanium balls are used and for large scale models billiard balls and bowling balls are used as although we consider them to be rigid, they are fairly elastic in the sense that they move for our mini Newton’s Cradle we’re going to use some wooden beads – although not as efficient they will work to demonstrate what is happening.
Materials needed for DIY Netwon’s Cradle
5 Wooden Beads
How to make your DIY Newston’s Cradle
Start of by cutting the shoe box to form a frame that the bead will be able to hang in – I used a kids shoe box for the model and cut out a frame from all 4 sides.
With the frame in place I measured how long each ball needed to be from the rim of the Frame in the case of ours around 10 cm
I then measured pieces of string 3x that length to ensure that there was plenty of room for knoting and making sure that beads could be adjusted
Taking 2 pieces of string per bead thread through and then tie securely.
Starting with the centre bead place it equal distance from each frame and secure to the frame with masking tape.
With the next bead on the left measure your length of string on one side and then put in place. Once it’s in place tape it with masking.
Then place the next 3 beads into place.
Check the alignment – this does take some tweeks to get them right and until they are exactly right in a straight line the model won’t work as well as a store bought Newton’s Cradle.
You can see in the picture above that with just a few of the balls our of line our video shows that they only follow the momentum through once and then it separates.
With adjusting you can get it to work – we managed to get ours to carry through a few times with fine adjustments.
The science bit
Newton’s cradle demonstrations the laws of motion particular those of conservation of energy and momentum. It also helps to understand friction. When the first ball is pulled up and let go the energy and momentum is transferred from that ball through to the other balls and to the end ball which will go out from the set of balls with the same speed as the first ball returning it will transfer that energy and momentum through the balls.
The balls do slow down over time this is because of loss energy due to friction and also elastic energy.
This post is part of the A – Z of Science Series organised by Frogs Snails and Puppy Dog Tails.