Question

Imagine that you fill a glass Coke bottle half-full of water and blow over the top. Remember the pitch. Tap the side of the bottle with a metal object (such as a table knife) and remember that pitch. Add more water to the bottle and try again. The pitch of the sound you hear when you blow over the top is higher than it was when the bottle was half full; the pitch you hear when you tap is lower. Using the basic principles of vibrations, waves, & sound, write a analysis explaining why there is a difference. • Why the blow is different from the tap • Why the pitch changes differently from the blow to the tap when more water is added

Answer 1

If the bottle is half filled sound waves are travels to the large distance from cap of the bottle to surface of water layer so there is a less intensity of sound similarly the bottle is completly filled sound waves travel to less distance so we hear more intensity of sound

Now if you had consider out side of the bottle

When the bottle is half filled in which the bottle remains half free so the sound waves easily can transfer with any appreciable loss if bottle is completely filled due to water molecules each molecule will absorb some of intensity of sound so ther could be loss of sound so we hear less amount of sound when tap outside the bottle

Based on vibrations :-

When the bottle is half filled more vibrations are produced because at free and antinodes are produced which are with maximum displacement and completely filled less vibrations are produced because nodes are formed which are less displacement