Method

The pellet gun is in a wooden case that is secured to a table with wheels so that it can not be moved. The gun and the table are positioned in front of a pellet trap that is 3 meters away and a string that is 2 meter away. This is aligned next to the wall which is covered with a black cloth for the background. The computer (Apple II plus) and the flashes (Vivitar 283) are on carts facing the gun and the string hanging from the ceiling. The camera (Nikon Coolpix 5400) is on a small tripod on the cart behind the flashes. Hanging from the string is the balloon filled with water and directly under it is a bucket to catch the water to minimize the mess.

We used a sound trigger which is regulated by the computer program Intervalometer 2. We input the delay time for the first flash and the three following flashes. Sound trigger is activated by the sound of the pallet gun firing. We developed the timing from calculations of the speed of the bullet which is ¾ the speed of sound and the distance from the sound trigger to the gun (approximately 2 meters). These times were entered in to the program Intervalometer 2. It regulated the delay of the flashes, so after the the gun went off the first flash would go off a certain amount of time later and then the remaining flashes would go off in sequence after that. The four input interface hooked the flashes, sound trigger and computer all together. Then we used trial and error to get the timing down so that we see two pellets before the balloon and two after the balloon. We used the flashes to show each image of the pellet traveling through air and the balloon. Each flash goes off in sequence to produce four different images in four different positions.

We started by setting up the pellet gun and getting it lined up with the pellet trap. It was set on three two by fours. We set up the computer and four flashes in front of the string that we were going to hang the water balloon. We had to figure out how long to make the delay for the first flash to go off and the delays for the remaining flashes. There was a problem with the last flash going off, because there was a problem with the cable so we got a new cable. A sound trigger made by Tatiana was used to set off the first flash. At first there was a problem with it going off, the battery was replaced and it worked fine. When we started shooting the pellets to test our delays, it was hard to see the pellets. We realized that it was because our black background was not far enough down, so the flash was reflecting off the white wall. We pulled the background down some and it helped out a lot. There was also some problems with the gun. The safety was not working and it was hard to open and close the slot that the pellet went into. This came from a piece that was connected to the gun. Dr. Winters removed it and the gun worked fine. When we started to take pictures of us shooting balloons we had a problem seeing pellets. We solved this by pushing the flashes up closer to the balloon, and opening up the camera’s aperture. Colored filters were put on the flashes to distinguish the different bullets. We took pictures and use them to change our delays to make sure we saw two bullets before the balloon and two leaving the balloon. We also realized that if the balloon is shot through the top or the center, it would not burst, but the pellet would just go through it and it will shoot out water. The balloon has to be shot through the bottom to get the right effect.