Free-Fall

Supplies:

2 liter plastic soda bottle

about 4 rubber bands

sharp thumb tack

2 discharged D cell batteries

paperclip

balloon

Construction:

Cut off and discard the lower two thirds of the soda bottle

With a hole punch, make two holes in the bottle, as shown

Make a chain of the rubber bands and thread them from the top of the bottle, into the first hole, out of the second hole and up to the top again, as shown above

Inflate a balloon inside the bottle, as shown above, and screw the top onto the bottle to hold the air inside the balloon

Using tape, attach the two batteries together.  These are used just for weight, so the polarity of the batteries does not matter

Use tape and the paperclip to make two hooks at one end of the battery.

Tape the tack to the top of the battery

Hang the batteries from the rubber bands.  Adjust things so that the tack is located just below the balloon.

Challenge:

If the bottle/balloon/battery system is dropped, when will the balloon pop?

Just below the point where the system is dropped?

Only when the system hits the ground?

At some other place?

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