A string is stretched between a fixed support and a pulley a distance 111 cm apart. The tension on the string is controlled by a weight hanging from the string below the pulley. An electomechnical vibrator is used to vibrate the string at 120 Hz. When the weight is adjusted to 275 g, the string is found to oscillate in its third standing wave mode (three loops). What is the speed of wave propogation on the string in this mode?

Question

Genevieve

Physics

19 July, 18:47

A string is stretched between a fixed support and a pulley a distance 111 cm apart. The tension on the string is controlled by a weight hanging from the string below the pulley. An electomechnical vibrator is used to vibrate the string at 120 Hz. When the weight is adjusted to 275 g, the string is found to oscillate in its third standing wave mode (three loops). What is the speed of wave propogation on the string in this mode?

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Jayleen Tran · Answer 1

88.8 m/s = Speed of wave propagation in the required mode. (3 loops)

Explanation:

When there are 3 loops.

the total length = L = 3 λ / 2

⇒ λ = 2 L / 3 = 2 (1.11) / 3 = 0.74 m

Velocity = v = f λ = (120) (0.74) = 88.8 m/s