Question

A string 2.0 m long and fixed at its ends is driven by a 240 Hz vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is ______.

Options

• 180 m/s, 80 Hz

• 320 m/s, 80 Hz

• 320 m/s, 120 Hz

• 180 m/s, 120 Hz

Answer 1

A string 2.0 m long and fixed at its ends is driven by a 240 Hz vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is 320 m/s, 80 Hz.

Explanation:

`(3lambda)/2 = 2` or `lambda = 4/3` m

Velocity, ν = f_λ = `240 xx 4/3 = 320` m/sec

Also f₁ = `240/3` = 80 Hz