The velocity v of the wave set-up by plucking a stretched string is found to depend on the tension T

Source: JAMB · 2023

The velocity v of the wave set-up by plucking a stretched string is found to depend on the tension T in the string, its length l and its mass m, and is given by v = kTx ly mz where x, y and z are unknown numbers and k is a constant. Find x, y and z.

The velocity v of the wave set-up by plucking a stretched string is found to depend on the tension T in the string, its length l and its mass m, and is given by v = kTx ly mz where x, y and z are unknown numbers and k is a constant. Find x, y and z.

  1. x = 1/2, y = 1/2 and z = – 1/2 ✓
  2. x = 1/2, y = 1/2 and z = 1/2
  3. x = 1/2, y = – 1/2 and z = – 1/2
  4. x = – 1/2, y = 1/2 and z = – 1/2
Explanation

Use dimensions. Speed v = L T⁻¹. Tension T = M L T⁻². So (M L T⁻²)ˣ Lʸ Mᶻ must equal L T⁻¹.

Time: −2x = −1, so x = 1/2. Mass: x + z = 0, so z = −1/2. Length: x + y = 1, so y = 1/2.

So x = 1/2, y = 1/2, z = −1/2.

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