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  4. Two pulses in a stretched string whose centres are initially 8 cm apart are moving towards each other as shown in the figure. The speed of each pulse is 2 cm/s. After 2 second, the total energy of the pulses will be <img class=img-fluid question-image alt=image src=https://cdn.tardigrade.in/img/question/physics/83b7d474f0fc2e2d943f5828b826ee8b-.jpeg />

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Q. Two pulses in a stretched string whose centres are initially $8\, cm $ apart are moving towards each other as shown in the figure. The speed of each pulse is $2 cm/s$. After $2$ second, the total energy of the pulses will be
image

Waves

Solution:

The two pulses are moving towards each other. The speed of each pulse is $2\, cm/s$
$\therefore $ After $2 \,sec$, one pulse moves to left by $4 \,cm$ and other pulse moves to right by $4 \,cm$.
$\therefore $ They superpose and annul the displacement of each other. The string will become straight
Hence there will be no potential energy
$\therefore $ The total energy of the pulses will be kinetic