Activity 16. Speed of a balloon rip
Note: Before doing this activity, try Problem 2 in Appendix F for practice. The photograph for that problem will also help in setting up the experiment.
- The setup for this activity is similar to that of the previous one. Inflate a large balloon and place sound triggers at both ends of it. Situate the clock disc above the front edge of the balloon and as nearly parallel to the film plane of the camera as possible. (See the photograph in Appendix F.) Place both flash units next to each other and just to the right out of the picture. The reason for this placement is so that the shadows cast by the rips will contrast with the rips themselves. Use the yellow automatic range, and close the lens aperture one stop from that indicated by the calculator dial. This corrects for the fact that the balloon will be illuminated by two flashes of light.
- Prepare for a photograph and puncture the balloon near the left end. Make an enlargement of the negative and determine the speed of the rip according to the method of Problem 2. (Remember, you will need to know the diameter of the clock disc.)
Note: If you take photographs
with a Polaroid camera, see Appendix
C for suggestions. In determining exposure, remember
that in this experiment each exposure results from two
flashes of light.