NSC 101 Laboratory for 2/10/98

Fluid Statics and Dynamics

This lab exercise consists of several stations. Carefully record all mesurements and observations at each station and write down your ideas ann explanations. Pay special attention to any questions.

STATIC PRESSURE

  1. Stack of Bricks: Pressure is force per unit area. Weigh the brick and measure its dimensions. Find the number of bricks, stacked on the largest face, that are required to produce an atmosphere of pressure (100,000 N/m2).
  2. The Hg Barometer: The pressure due to the atmosphere will support a column of mercury about 76 cm high. Measure todays atmospheric pressure with the Hg barometer in cm of Hg. Convert to N/m2 and lb/in2. How high would the column be today if a water barometer was used?
  3. Vacuum: Turn on the vacuum pump to remove the air from the bell jar and observe what happens to the various objects inside. Next, connect the hose from the pump to the Magdeburg hemispheres and evacuate the air inside. Try to pull the hemispheres apart without twisting. Assuming a complete vacuum inside the sphere, estimate the force needed to do this.
  4. Snorkeling: Your lungs draw air in by expanding the chest and thus creating a pressure differential between the lungs and the outside. You can measure the maximum pressure differential of your lungs by submerging yourself in water and finding the maximum depth at which you can breath through a snorkel tube. The dry version of this experiment is to draw a column of water up a tube using your lungs. Find the maximum pressure differential, in atmospheres, of your lungs using the tube and water reservoir. (Be sure to use only your lungs, not the pump action of your mouth.)
  5. Standpipes: Observe the levels of water in the standpipes. Can you offer an explanation as to why the water is higher in the smaller pipes?
BUOYANCY
  1. Archimedes Principle: Weigh the rock and the small empty displacement jar using the spring scale. Completely fill the large container with water and place the small displacement jar below the pouring lip. With the spring scale, carefully lower the rock into the large container such that the water flows into displacement jar. With the rock not touching the container, record the scale reading. Find the weight of the displaced water. Find the % difference between the buoyancy force and the weight of the displaced water. Do your results confirm Archimedes Principle?
  2. Floating: Try floating the various objects on the towel next to the fresh water aquarium. Explain which objects float, which do not, and why. (Place the objects back on the towel to dry when finished.) What effect might salt water have on this experiment? What if you performed this experiment of the moon?
  3. Cartesian Diver: The cartesian diver consists of an eyedropper with a bubble trapped inside. Squeeze the bottle and observe the diver. Explain what happens. Does it matter where you squeeze the bottle?
FLUID MOTION
  1. Coin in the Box: Flip the coin into the box by blowing over the top of the coin. Use a piece of paper or tape to block the front edge of the coin to assure that air is not lifting underneath the coin. Explain this trick.
  2. Card and Spool: Hold the card gently to the bottom of the spool and blow forcefully down through the hole. If you slowly remove your hand while blowing, the card will stay in place. Explain using a diagram showing the airflow.
  3. The Trapped Ball: Turn on the air blower and place the styrofoam ball just above the outlet. Gently nudge the ball and observe the stability in the airstream. It should be possible to tilt the air blower considerably without the ball leaving the airstream. Explain using a diagram showing the airflow. Specifically, why the ball is in stable equilibrium.
  4. The Tornado: Turn the tornado device over, swirl the water rapidly for a few seconds, and then place the device on the table. Explain what you see. Explain what conservation laws might apply. Why is there a "hole" in the center? (In an actual tornado, the hole is a very low pressure area that is responsible for exploding houses!)
  5. The Siphon: Release the valve on the siphon tube and move the end of the tube to different points below the level of the water in the tank. Observe the velocity of the water exiting the tube as the position changes. Explain the results qualitatively. Is there a limit to the height of the highest portion of the tube?