Visualizing Newton’s Cradle
Using spheres as switches to reflect the connect/disconnect change.Rebecca Zhou, Sep 17, 2019
The concept of this switch is inspired by Danny Rozin’s demonstration on the class, which he gently blowed to the aluminum foil to let it be connected with the whole circuit. The idea behind it, from my perspective, is that the circuit can be a good visualization tool to reflect subtle changes in real life. So I began to think about what kind of subtle changes can be visualized creatively.
I noticed I had a Newton’s Cradle in my room. It was a classic experiment to test the Newton’s third law. However, the middle three spheres won’t always stay still when the first one swings and strikes the middle ones. It occurred to me that I can visualize the hitting process (the losses of momentum) by connecting these balls as parts of the circuits.
The original idea was as follows.
When I had my first try, it turned out that the connections between balls are not completely conductive. It had larger resistance than I thought. So the ideal circuit modified to be like this.
I used 5V breadboard power output to confirm the circuit worked. Next thing to do was to measure the resistances and LEDs among balls to calculate the voltage and protective resistors that could light up the LEDs safely.
Due to the moisture and unstable contact between balls, the resistances changed a lot. I used 9V battery to supply power. To secure the LEDs not to be burnt, I add protective resistors for each LED. Unfortunately, I couldn’t measure the resistances of LED, not knowing if I incorrectly used the multi-meter or just it was broken. I estimated them and add 10kΩ for the outside LEDs, 220 for the 2nd and 4th, 570 for the middle one.
After completing the circuit, the lights could be lit up when they hit each other. But the lights were dim due to the small contact area between balls. So I dipped some water on the balls to let them be more conductive and enlarge the contact areas.
4 Work Demo
I originally wanted more fancy effect like controlling to play different layers of the music using spheres as switches, to create orchestra-like sound effect. Each layer of instrument will play if this layer of circuit be connected. However, I only had one speaker (not 5) and the battery didn’t have enough power to drive the speaker.
More spheres will create better demonstration how momentum losses during the strike process. 5 is just a little bit less.