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According to the formula $λ=h/mv$ for the De Broglie wavelength, as the mass increases, it becomes a greater coefficient to multiply the velocity by, and the larger number in the denominator makes the wavelength so small that it can't be detected for high mass objects. My physics teacher used this reasoning to explain how even large macroscopic objects may have their own wave functions, but are so small we can't really detect them.
However, aren't all larger objects made of smaller ones? Like how molecules are made of atoms, and atoms are made of the elementary particles, and etc. Since this is the case, why can't we apply the λ=h/mv formula to all the particles that make up the atoms and molecules that are inside of say, a baseball, and average find the average of those waves? Since on average, half of those waves should be constructive, and the other half destructive, shouldn't the average of all the waves of the particles that make up the larger object be the true wavelength of the object? This obviously isn't the case though, since a baseball doesn't exhibit wave-like behavior.
What's the flaw in my reasoning? Why don't high-mass objects behave like I expect them to? I tried to read the Wikipedia page on the wave-particle duality, but I still haven't been able to come to a conclusion.