Gravity and Resistance
My project was to demonstrate that two objects fall at the same rate when placed in a vacuum. This shows the effects of gravity as well as what happens when there is no air resistance in play. This was accomplished by placing two objects of different masses and sizes into two long plastic tubes and taking the air out of both of the tubes. When the tubes were flipped upside down, the two objects hit the bottom of the tube at the rate of gravity.
Air Ejector
An air ejector was used to take the air out of the tubes. This machine is based on the ejector-venturi principle that passes motive air or gas through a convergent nozzle. The convergent nozzle then converts pressure into velocity which creates a vacuum within the body chamber to draw in and entrain gases. The motive gas and suction gas are then mixed and passed through the diffuser tail. The nozle throat diameter controls the amount of air or gas that passes through. As the tbe narrows, the velocity of the fluid increases as the pressure decreases and a vacuum occurs as per Bernoulli's theorem P1V1= P2V2. Essentially, what happens is that the momtion of moving fluid (which we call the motive fluid) is used to trasport another fluid (called the suction fluid).
The Seal
To create an air tight seal on the plastic tubes to prevent any air from leaking in, certain pieces of equipment were used. O-rings were used in between the plastic tube and the rubber stopper . They are designed to be compressed between two or more parts creating a seal at the interface. Rubber stoppers (also called rubber bungs) were used to keep the plastic tubes sealed so that liquids or gases cannot escape or enter. A hole was drilled into the top of the stopper to be able to insert the valve. Valves are a device that regulates, directs or controls the flow of a fluid. When the valve is open, the fluid will low from an area of high pressure to an area of low pressure.
Apparatus
A six foot long plastic tube was used in this project. A hand saw was used to cut the tube in half so each tube was 3 feet long. The tube has an outer diameter of 1.25 inches and an inner diameter of 1 inch. We had to be careful of the size and length as we needed a sturdy tube that can withstand the pressure of the vacuum. A long metal rod was used and metal bars and clasps were used to hold the tubes connected to the rod. The design was that the two ends of the rod would sit on two separate tables so the tubes will be abe to be flipped forwardto allow the objects within to fall from one end to the other.
The Project
NASA: Ball and Feather Drop
The objects that were used inside the tube were a small rock and cardboard paper. The metal rod had loose clasps wrapped around it that allowed the metal bar to rotate around it. The metal bar and the clasps were help together using bolts, washers and nuts. The tubes were placed into the metal clasps and tighened into place using the bolt and nut. The two ends of the metal rod were placed on same level desks to be flipped upside down and right side up easily.
The result of the construction of this experiment was that there was great difficulty in getting the objects to not hit the sides of the tube when they were falling from one end of the tube to the other. This created interference and prevented the experiment from working but after a couple tried and a couple flips, the effects can be seen in the vacuum. The two objects of different size and mass do fall at the same rate in a vacuum!
NASA has rececnty tried the same thing to a much greater extent and also with much greater results. They built the world's largest vacuum where they dropped a ball and a feather from the ceiling of the room and let them both fall to the ground. It can be seen that the object both hit the ground at the same time.
FIGURE 1: shows the workings of an air ejector. (image taken from Wikipedia)
FIGURE 2: (left) shows o-rings. (top) shows rubber stoppers. (bottom) shows open and closed valves. (images taken from Wikipedia and How Stuff Works)
FIGURE 3: (left) shows the clear plastic tubes used. (cecnter) shows the metal rod. (right) shows the metal bars and clasps. (image of own experiment)
VIDEO 1: Shows NASA doing the ball and feather drop in a vacuum chamber. (video taken from https://www.youtube.com/watch?v=E43-CfukEgs)