Untitled Document

Physics Demo Number: 067

Approximate Run Time: 5 min

Water-filled Plastic Soda Bottle Tossed Up For Free Fall

Demo Description

A soda bottle with a hole in its side and in its top will not lose water while tossed up into the air, even when it pauses instantaneously before coming down. This shows that the bottle has acceleration equal to “g” during the entire out-of-hands experience.

Scientific Principles

Newton's Laws of Motion
Gravitational Acceleration
Hydrostatic Pressure goes to Zero During Free Fall

Equipment & Set Up

20 oz soda bottle

Equipment Location

The bottle is located in Kit (067) on [F-2-5]

Instructions

One takes a 20 oz soda bottle and manufactures a hole in its side about midway down, as well as placing a hole in it cap.

Fill the bottle with water, with a finger plugging the side hole, and screw its top back on.

Show that removal of the plugging finger gives a nice stream of water out of the side hole.

Now toss the bottle upwards.

Observe that no water streams out until the bottle comes back to stable rest ( hopefully back in the tosser's hands).

In particular the bottle emits no stream even when it instantaneously ceases its vertical rise to start back downwards again.

One may thus conclude that the bottle has acceleration equal to “g” during the entire out-of-hands experience, even at the apex of its vertical excursion.

This constitutes direct experimental contradiction of the conventional student gem of wisdom that if velocity is instantaneously zero at top, acceleration must also be zero instantaneously at the top.