Two open organ pipes of lengths and are sounded together before a stationary listener

PHYSICS · Single correct · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics

Problem

Two open organ pipes of lengths

0.85\,\text{m}

and

0.80\,\text{m}

are sounded together before a stationary listener. The shorter pipe is then moved directly away from the listener with speed

u

. The beats disappear and the two notes are heard in unison. Determine

u

. (Speed of sound in air

=340\,\text{m\,s}^{-1}

.) (a)

10.6\,\text{m\,s}^{-1}

(b)

20.0\,\text{m\,s}^{-1}

(c)

21.3\,\text{m\,s}^{-1}

(d)

34.0\,\text{m\,s}^{-1}