Physics Demo Number: 009

Approximate Run Time: 15 min

Free Fall at Constant Acceleration

Demo Description

Free fall at constant acceleration  is illustrated by the following methods.

 


  • Dropping of weighted chains - verified audibly.

  • Water streaming or not-streaming from a bottle tossed into air.

 

Scientific Principles

  • Constant acceleration is observed for objects with only gravity acting on them.

Equipment

  • Rock-climbing accessory cord with fishing weights. 

  • Pop bottle.

  • Round metal ring  anchored to  dark green  accessory cord.

  • Carabiners and swivel which can be used  in place of ring to attach to dark green accessory cord.

  • Round metal ring  anchored in ceiling and intersecting closed loop of  the green accessory cord.

Equipment Location


  • Round metal elevating ring lives in Kit(009) .

  • Elevating Carabiners with swivel live attached to 2X4 from demo(008).

  •  Kit(009) aka Kit(067) on [F-2-5].

  • Cans with weighted cords attached are in Kit (009).

  • Elevating ring or biner will be called elevating attachment point for brevity.

 



 

Instructions




The photos show apparatus for illustrating free fall and constant acceleration. The fourth photo shows the biner variation of attachment point .

Two long (35 or 40 feet) pieces of rock-climbing accessory cord that have five large and one small fishing weight attached to each are seen in the first photo.

The light- green cord has the weights tied at linearly increasing multiples of the spacing of the first weight from the small -locating-weight end.

The orange cord has its five large weights tied such that the second one is at 4 times the distance of the first, the third at 9 times ,…, the fifth at 25 times the distance of the first from the small-locating-weight end.

The  dark green cord( seen in photos 2 and 3) :

     1) is permanently closed- looped through the ring in photo 2 (which is fastened to the lecture hall ceiling). (Please do not under any circumstances untie this closed loop!)

      
     2) can be  tied to either elevating attachment point . 

When  one of the fishing-weight- loaded cords seen  in photo 1 is threaded through  an elevation attachment point as shown schematically in the diagram below photos 1 and  2 for the ring elevator, then that loaded cord may be raised to ceiling level by rotating the cord tied to the ring to raise the ring  while paying out loose line  on the weighted line to keep its'  appropriate weight ( i.e. the one which is 5 or 25 times the locating distance  from the weighted end) at the level of the ring.

When the fifth  large weight on the light-green-cord is raised about 16 feet above the floor , one may release the end of the unweighted half of that cord to allow the weights to free fall onto a  metal shelf on the floor.

The careful listener will discern an increasing tempo of collision noises in this case.

The orange cord produces an even tempo of collision noises (one about every fifth of a second).

A pop bottle  has a hole in its side and another in its lid, so that when filled with water and both holes opened a nice stream is emitted from the hole in the side.

However, if the bottle is tossed up into the air, no water streams out during the entire free fall motion of the bottle, especially not at the top when the velocity is instantaneously zero.
  
Writeup created by David A. Burba
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