A can of spray paint is attached to a spring oscillator. A sheet of paper towelling is run past the oscillating can. The result is a sine wave on the paper.
1. spray paint oscillator cart
2. bright color spray paint
3. roll of brown paper
4. plastic tarp
5. duct tape
You may need to lock the wheels of the cart. The cart can roll as the rope is being pulled.
Unfurl the tarp and roll the cart on top of it. Assemble the spray paint oscillator by attaching the long vertical rod to the cart. Hook the bottom of the spray paint/spring system to the hook on the bottom of the cart, making sure that the can does not touch anything while hanging at equilibrium. Adjust the height of the spring system such that the amplitude of oscillations does not exceed the limits of the paper. Wrap the paper around the cart and tape it to the left-most pole. Wrap the rope around the pole such that the pole turns clockwise when the rope is pulled. To perform the experiment, screw the nob to activate the spray paint and displace the can to create oscillations. Pull the rope steadily to create a sine wave on the paper. Turn off the spray paint. Optionally, tear the paper and tape it to the wall/black board for the class to see.
This is a demonstration of simple harmonic motion. The can of spray paint on a spring is a simple harmonic oscillator. It's displacement as a function of time can be described by a sinusoidal function. By running the spray paint over a length of paper, we are "graphing" displacement vs. time.
Special Cart, usually in 26-003
See page 419, University Physics, for information regarding periodic motion.
Young, Hugh D., Roger A. Freedman, and A. Lewis Ford. Sears and Zemansky's University Physics: With Modern Physics, 12th ed. San Francisco: Pearson Addison-Wesley, 2008.