Fascinating. Mesmerizing. You can stare at it for hours. Play with it all you want. This device demonstrates the conservation of energy and momentum. When you swing one ball and it knocks into the next, it will transfer the energy from one ball to the other. Of course, we do have some real world friction and chafing from the paracord so that might prove to be an irritant and affect the performance somewhat.
This version of the Newton's Cradle consists of an uneven number of balls in a linear formation which are suspended by paracord from a structure that lets them swing freely between such supports.
I would think every Science teacher like Instructables member Kiteman or those of the scientific mind should have one handy to demonstrate some fundamental laws of physics.
Disclaimer: Ahem, it failed to perform as expected. But don't let this stop you from having a good time building it, only make the necessary changes described in the text.
Please, no Fn comments on this instructable, this is something completely different. The following instructable contains discussion of a frank nature and may not be suitable for all. Pun accordingly.
Step 1: Materials on Hand...
For this project you need...
* Paracord or similar string/twine/rope
Hey, I found some paracord in cool Instructables reddish/orange.
* An odd pair of balls - dense spherical objects - should be an uneven number like 3 or 5. I used golf balls, you will be might be lucky enough to have ones made of brass. There do exist Newton's Cradles made with bowling balls so size does matter.
* Tape to cover the golf ball if needed
* Two dowels, sticks, pencils, chopsticks or drumsticks to use as horizontal support rods
* Cardboard and glue for the support structure.
* Picture of your favorite character for decoration.
Step 2: Pump It Up...
Make a monkey's fist...monkey's fist knot.
In keeping with the paracord theme, I could have just put in a screw eye or drilled out a hole to pass through the paracord in the golf ball but I chose to make a monkey's fist knot to encase the golf ball. This method of attachment inteferes with the action of the balls and should not be used if you want to build a fully functional Newton's Cradle. The golf balls are used as the core of a monkey's fist knot.
You can check out the various monkey's fist knot instructables to learn how to make a monkey's fist knot. It is actually simple but difficult to execute so I read up on a few instructables to see how it is done. It does take a lot of practice make one.
The only tip I will offer is that I wrapped the golf ball with tape over and under to make it a sticky ball. The golf ball was just too slippery to use for the core as the paracord just moved around too much.
I'll just include photos on how I did a monkey's fist knot. You can do more turns or wraps in each direction to get better coverage but I only did three just to tie the golf ball down.
Use a piece of paracord that is about 4 feet long for each ball.
You can seal and keep the cut ends from fraying by just sticking it quickly into a flame - carefully and melting the ends. Make sure you give it a chance to cool or you will burn yourself. Which reminds me, who is the bravest man in the world? That chestnut roaster in the winter...he whistles while his nuts are burning.
You should end up with a golf ball that has two leads coming from the center.
Try to get the knot as tight as possible by taking up the slack of each winding. You may need something to pick out the cord so you can pull on it.
Step 3: You Need Support...
For the support structure you can use two broom sticks and hang it across the backs of two chairs.
I made my support stand or "cradle" from cardboard and two drumsticks.
For the base I had the bottom of a cardboard box that seemed to be the right dimensions.
I cut out vertical supports about 14 inches high.
Laminate and glue 3 layers of cardboard with the internal corrugations going in different directions for greatest strength.
When they are dry, line them up and punch a hole in each support to hold your horizontal supports. I used a screwdriver to poke through the cardboard and force fit the drumstick through.
The supports should be able to hold the sticks level.
Glue the supports to the sides of your cardboard tray or base. If you don't have a nice tray-like box to use, just fabricate one from other pieces of cardboard.
Step 4: So How They Hanging?
You should wait for the glue to dry before you apply any weight or pressure. If desired, you can lash together the horizontal supports like a set of gymnast's parallel bars.
I used an ordinary clove hitch to secure the end of the cord to the crosspiece. There are many knot instructables that show you how to tie this simple knot.
Attach all of the balls to the two crossbars loosely at first. You will need to make some adjustments.
Ideally, they will be hanging low and loose but adjust the length of both cords to be even and tighten up the knot. The spacing on the support bars should also be evenly spaced apart. The balls should be swinging comfortably and not restricted from movement.
Look down the end and make sure all of the balls are in alignment, one should not hang lower than the other but it may occur. They should also contact each other with no gap in between.
I tried to move the paracord out of the spot where the balls make contact but that seemed to distort the monkey's fist knot too much where the ball would slip out.
Once everything is aligned, wrap any excess cord around the support and secure with a clove hitch.
Step 5: Does It Perform?
You can click on thei image button on the last image to download the graphic if desired.
Scale it to appropriate size and print out. Glue to a piece of stiff cardboard. Cut out and attach to your Newton's Cradle.
So in this "experiment", paracord seems to act as a shock absorber which is an effect we do not want. The inherent stretch in the suspension cords may also impact negatively. If you look closely in the video, perhaps three balls only might have worked.
You can further research Newton's Cradle and the scientific principles behind it.
For now, just grab a few balls, pull it back, and let go. Observe and learn. Repeat.
If you want it to work, use the purple cord and do not use the monkey's fist to hold the balls.
Have fun in working it.