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snoopies622
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If a ball with mass [tex]m_1[/tex] moving at speed [tex]v[/tex] strikes another ball of mass [tex]m_2[/tex] that is initially at rest in a head-on elastic collision, the speeds of the two balls after the collision are
[tex]
v_1 = v (\frac {m_1 - m_2}{m_1 + m_2})[/tex], [tex]v_2 = v (\frac {2 m_1}{m_1 + m_2})[/tex] respectively.
If a wave with amplitude A moving in a medium with speed [tex]v_1[/tex] hits (head-on) the boundary of another medium in which it moves at speed [tex]v_2[/tex], the amplitudes of the reflected and transmitted waves are
[tex]
A_1 = A (\frac {v_2 - v_1}{v_2 + v_1})[/tex], [tex]A_2 = A (\frac {2 v_1}{v_2 + v_1})[/tex] respectively.
And if instead of speed one defines a variable that is inversely proportional to it, as in
let [tex]k_1 = 1/v_1[/tex] and [tex]k_2 = 1/v_2[/tex] then for the waves we get
[tex]
A_1 = A (\frac {k_1 - k_2}{k_1 + k_2})[/tex], [tex]A_2 = A (\frac {2 k_1}{k_1 + k_2})[/tex]
which look exactly like the equations for the colliding balls.
Since balls are not waves and mass is not speed (or the inverse of speed), why are these formulae isomorphic? I know that wave-particle duality is a central idea in quantum mechanics, but these relationships are derived using classical assumptions, and rather different-looking assumptions at that; conservation of momentum and kinetic energy in the first case and continuity and differentiability of waves at a boundary in the second. Is it a coincidence or is there something deeper at work here?
[tex]
v_1 = v (\frac {m_1 - m_2}{m_1 + m_2})[/tex], [tex]v_2 = v (\frac {2 m_1}{m_1 + m_2})[/tex] respectively.
If a wave with amplitude A moving in a medium with speed [tex]v_1[/tex] hits (head-on) the boundary of another medium in which it moves at speed [tex]v_2[/tex], the amplitudes of the reflected and transmitted waves are
[tex]
A_1 = A (\frac {v_2 - v_1}{v_2 + v_1})[/tex], [tex]A_2 = A (\frac {2 v_1}{v_2 + v_1})[/tex] respectively.
And if instead of speed one defines a variable that is inversely proportional to it, as in
let [tex]k_1 = 1/v_1[/tex] and [tex]k_2 = 1/v_2[/tex] then for the waves we get
[tex]
A_1 = A (\frac {k_1 - k_2}{k_1 + k_2})[/tex], [tex]A_2 = A (\frac {2 k_1}{k_1 + k_2})[/tex]
which look exactly like the equations for the colliding balls.
Since balls are not waves and mass is not speed (or the inverse of speed), why are these formulae isomorphic? I know that wave-particle duality is a central idea in quantum mechanics, but these relationships are derived using classical assumptions, and rather different-looking assumptions at that; conservation of momentum and kinetic energy in the first case and continuity and differentiability of waves at a boundary in the second. Is it a coincidence or is there something deeper at work here?
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