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Liquid Pressure

Materials Required:

Three to four transparent plastic bottles of different capacities (2 litre, 1.5 litre, 1 litre and 0.5 litre),Nail or compass to make holes in the bottle, Cello tape, Meter scale, Paper cup or glass tumbler, A wooden stool or table to be used as a stand, Water

 

Procedure:

Real lab procedure:

  • Take three or four transparent plastic bottles of different capacities.
  • Make one hole on the side of each of the bottle at the same distance from the base of the bottles.

     

     

  • Seal these holes with cello tape.
  • Mark a point near the top of the bottle of the least height.
  • Measure the height of this mark from its bottom.
  • Make marks at the same height in the remaining two bottles also. Fill each bottle with water using a paper cup or a glass tumbler up to the mark. Count the number of cups used to fill each of the bottles. Note that the level of water is the same in all the bottles.
  • Place one of the bottles on the wooden stool or table.
  • Remove the cello tape from the hole. The water stream will come out of the hole.

     

     

  • Mark the point at which the water stream falls on the floor.
  • Measure the distance of this mark from the base of the stand.
  • Repeat the same steps with all the bottles and tabulate the reading in a table. Make sure to place the bottles at the same position on the stool every time.
  • Try out the same experiment taking different level of water in each bottle. Also check what will happen if you make 3 holes at different height on the same bottle and allow the water streams to come out.

 

Simulation procedure:

  • Select the hole positions (Top-Middle-Bottom) by clicking on the slider corresponding to bottle numbered 1, 2 and 3.
  • Drag and drop the cello tape towards bottle 1 to seal the hole in the bottle.
  • Repeat the steps for bottle 2 and 3.
  • Drag and drop the container to pour water into the bottle 1.
  • Repeat the steps for bottle 2 and 3.
  • Observe that the water is filled up to the red marking in each case. Notice that the water level is equal in each of the three bottles.
  • Click on the 'Remove cello tape' button to remove the cello tape from the bottles.
  • Observe and note down the distance at which water stream falls on the floor.
  • Read the inference message.
  • To redo the experiment, click on the ‘RESET’ button.
  • NOTE: Click on the HELP button if you need help.

Observation:

Bottle Distance of the mark from the stand (cm)
   

 

 

 

 

 

  • In first case, though the volume of water in different bottles was different still the distance at which the water stream from the holes hit the ground was almost the same for every bottle.
  • When holes are made at different height on same bottle, the water emerging out of hole at the bottom falls at larger distance. This is because the liquid column exerts the pressure on the bottom and this increases with the height of the liquid column.

 

Conclusion:

The liquid pressure depends only upon the height of the liquid column and not the volume of the water in the container.