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Object: To show that objects fall at same rate in the absence of air resistance.
Discussion: Before class starts, make sure the vacuum valve is closed and the pump is turned on. When class starts, drop the billiard ball and feather simultaneously from your hand. Of course the billiard ball strikes the ground several seconds before the feather gently lands. Perhaps this is because the billiard ball weighs much more than the feather... Connect the power supply to the electromagnet leads and increase current to 1.5A. Close the shelf and place the feather on the shelf. Place the washer on the shelf and center the billiard ball on the washer. After centering the top flange on the vacuum chamber, slowly open the vacuum valve being careful not to 'blow' the feather off the shelf. After about 15 minutes, turn off the electromagnet and watch the feather and billiard ball reach the floor simultaneously.
Stolkin: In Stolkin, aiming the video camera toward the bottom third of the chamber makes the demo easier to observe for those sitting in the rear. You can video tape the demo and play back the video frame by frame to convince those that do not believe the two objects hit bottom simultaneously. Remember to increase the lighting and the shutter speed of the camera to 1/500 sec.
Equipment:
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