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In Figure. two pulses travel along a string in opposite directions. The wave speed v is 2.0 mls and the pulses are 6.0 cm apart at t =0. (a) Sketch the wave patterns when t is equal to 20 ms. (b) In what form (or type) is the energy ofthe pulse at t= 15 ms? |
Answer» SOLUTION :At t = 0 sec  (a) At t = 20ms. Distance travelled by the first pulse in 20 ms is `= Vt =2xx 20 xx 10^(-3) = 4cm`. Distance travelled by the second pulse in 20 ms is also `= Vt =2xx 20 xx 10^(-3) = 4cm`  (b) At t = 15 ms, by the principle of SUPERPOSITION resultant wave DISPLACEMENTIS zero. Hence, the shape of the string is straight at t = 15 ms. Hence, total energy is purely kinetic.  t = 15 ms. |
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