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Methods
Equipment Used
Equipment Setup
In order to maintain a constant force when we flipped the penny, we created a penny launcher. We made the penny launcher in the following way: We screwed the spring launcher at a slight angle into a board. We then screwed in another board perpendicular to the base board, on top of which we could place the penny, very close to the spring launcher, so that when we release the spring launcher, it would hit the underside of the penny. We also cut off 2 pieces of metal, with a hole on each piece to secure our photogate trigger. We duct taped the 2 pieces of metal, one on each side of the vertical board. When the spring launcher hits the underside of the penny, flipping it into the air, the penny will break the ultraviolet beam that the LED emits. When the PT no longer receives the ultraviolet beam because the penny has interrupted it, a signal will be sent to the input box (PB Port), located on a table, to the right side of the penny launcher, alongside the Apple II+. This signal is then relayed to the Apple II + Computer Intervalometer program, Multiplexer, which has preset values of time delay and intervals for flash units. The computer then sends signals to a blue output box, located on the table alongside the computer, after a preset time delay. These signals travel from the output box to the 8 flash units on a nearby table via separate cords, discharging each flash after a preset interval of time. The 8 flash units were lined up in a row on a table facing the penny launcher and were approximately .5m away from the penny launcher. The table on which the flashes laid, was raised about .5m from the ground, above the penny launcher so as to light the penny at the top of its trajectory. The Minolta Dimage Z1 Camera was secured on a tripod behind the flash units, slightly above the row of flashes. The distance from the camera to the penny launcher is .75m. In an attempt to ensure that the same amount of force was applied to the penny, we attached two metal rods to the vertical board to indicate how far down one needed to pull the spring. The two rods were about 6 cm apart. We chose to take data with two different forces being applied so we could see if the amount of force impacted the outcome. The force level that is indicated by the higher rod will be referred to as Force 1 and the lower rod will be called Force 2. The camera was raised to a height of 1 meter for Force 1 and 1.5 meters for Force 2, so as to capture the penny at the top of its trajectory. Behind the penny launcher, a black backdrop provided a dark, simple background.
Fig. 1-1
Fig. 1-2
Triggering, Timing, and Imaging Methods
In order to capture an image of the penny's trajectory we needed several flashes to illuminate the penny at regular intervals. To do so we used Multiplexer, a program which allows the user to set an initial delay time as well as a time for the flash interval. We connected eight flashes to an output box which was connected to the gameport of the Apple II+. We decided that the best trigger to use for this program would be a photogate whose beam could be broken by a launched penny. We could not find an existing photogate that we could mount on our launcher so we built a custom one. We attached the PT and LED on opposite sides of our launcher so that the beam between the PT and LED would be broken when a penny was launched. When the penny broke the beam, the trigger sent a signal to computer and Multiplexer initiated the sequence of flashes through the output box.
We set the initial delay at 150ms with 50ms intervals for Force 1 and increased the initial delay to 200ms for Force 2.
We used a Minolta Dimage Z1 digital camera in manual mode to capture our images. We used a shutter speed of 1.6 seconds and apertures ranging from f-5.6 to f-8. We used eight flashes to capture multiple exposures of the penny and gain an understanding of the penny’s trajectory. The long shutter speed allowed time for the photographer to communicate to the launcher that the shutter was open and for the penny to be launched.
Experimental Method
We checked our equipment to ensure that the trigger set off all of the flashes. We painted the tails side of the penny pink with fingernail polish to attain a clear visual distinction between the sides. After turning out the lights and turning the brightness of the computer screen down, we hit the 4 key which calls the flashes to go off once the beam is broken. The photographer opened the shutter and signaled to the launcher that the shutter was open and the launcher released the spring, sending the penny into the air. This was repeated twenty times: ten times at both of our force levels, five of which originated tails up, five of which originated heads up.
