======Dropping Coin and Feather in a Vacuum======


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**Alternative titles:** Galileo’s Falling Objects Demo
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====Summary====                   
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====Procedure====  
  -Begin with a transparent rigid plastic tube filled with air. Hold it vertically and let the coin and feather fall. Point out that the feather drifts down much more slowly.  
  -Attach the vacuum pump to the tube and evacuate the air until the pressure is very low. Close the valve and disconnect the pump.  
  -Hold the tube horizontally and gently shake so the coin and feather rest side by side on the inner wall.  
  -Quickly rotate the tube to vertical and observe both objects falling at the same rate.  
  -Optionally, allow some air back into the tube and repeat to show how increasing air resistance changes the feather’s fall.



====Links==== 
Dropping a Feather and a Coin in a Long Vacuum Chamber—Gravity Demonstration - The Action Lab: 
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Brian Cox visits the world's biggest vacuum | Human Universe - BBC: 
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📄 Coin and Feather - Jeff Rudd: [[https://www.sfu.ca/phys/demos/demoindex/mechanics/mech1c/coin_and_feather.html]]\\

📄 Falling Feather - Exploratorium: [[https://www.exploratorium.edu/snacks/falling-feather]]\\

====Variations====
  * Replace the feather with a light object such as a packing peanut or small piece of paper.  
  * Demonstrate with partial evacuation to show the gradual effect of reduced pressure.  
  * Compare the classroom version with a video of Apollo 15’s feather-and-hammer drop on the Moon.  
  * Record the experiment with a slow-motion camera for clearer viewing.



====Safety Precautions====
  * Only trained individuals should handle vacuum equipment.  
  * Rotate the tube smoothly to avoid the feather sticking to the walls.  
  * Ensure the seals and connections are secure to prevent sudden leaks.  
  * Do not use fragile glass tubing; plexiglass or acrylic is safer.




====Questions to Consider====
  * Why does the feather fall more slowly in air but not in a vacuum? (Air resistance slows it, but in a vacuum only gravity acts.)  
  * Why doesn’t the heavier coin fall faster than the feather? (Gravity pulls harder on the coin, but its larger mass resists acceleration equally, so both accelerate at the same rate.)  
  * How does this demonstration connect to Galileo’s experiments and the Apollo 15 mission? (It confirms that without air resistance, all objects fall equally fast regardless of mass.)  
  * What is terminal velocity, and how does it explain the feather’s slow fall in air? (It is the speed at which air resistance balances gravity, preventing further acceleration.)