JEE Challenger
More from Waves

Separation Between Successive Nodes on Vibrating Stretched String

A 20 cm20\text{ cm} long string, having a mass of 1.0 g1.0\text{ g}, is fixed at both the ends. The tension in the string is 0.5 N0.5\text{ N}. The string is set into vibrations using an external vibrator of frequency 100 Hz100\text{ Hz}. Find the separation (in cm\textbf{in cm}) between the successive nodes on the string.

Official Numerical Answer5

Topics & Concepts

Step-by-Step Solution

To find the separation between successive nodes on the vibrating string, we follow these steps:

  1. Calculate the Linear Mass Density (μ\mu):
    The mass of the string is m=1.0 g=1.0×10−3 kgm = 1.0\text{ g} = 1.0 \times 10^{-3}\text{ kg}, and its length is L=20 cm=0.20 mL = 20\text{ cm} = 0.20\text{ m}.
    μ=mL=1.0×10−3 kg0.20 m=5.0×10−3 kg/m\mu = \frac{m}{L} = \frac{1.0 \times 10^{-3}\text{ kg}}{0.20\text{ m}} = 5.0 \times 10^{-3}\text{ kg/m}

  2. Calculate the Speed of Transverse Waves (vv):
    The tension in the string is T=0.5 NT = 0.5\text{ N}. The wave speed vv is given by:
    v=Tμ=0.5 N5.0×10−3 kg/m=100=10 m/sv = \sqrt{\frac{T}{\mu}} = \sqrt{\frac{0.5\text{ N}}{5.0 \times 10^{-3}\text{ kg/m}}} = \sqrt{100} = 10\text{ m/s}

  3. Calculate the Wavelength (λ\lambda):
    The string is driven by an external vibrator of frequency f=100 Hzf = 100\text{ Hz}. The wavelength λ\lambda of the wave formed on the string is:
    λ=vf=10 m/s100 Hz=0.10 m=10 cm\lambda = \frac{v}{f} = \frac{10\text{ m/s}}{100\text{ Hz}} = 0.10\text{ m} = 10\text{ cm}

  4. Calculate the Separation Between Successive Nodes (dd):
    In a standing wave, the distance between any two consecutive nodes is equal to half of the wavelength:
    d=λ2=10 cm2=5 cmd = \frac{\lambda}{2} = \frac{10\text{ cm}}{2} = 5\text{ cm}

(Note: The fundamental frequency of the string is f1=v2L=102×0.20=25 Hzf_1 = \frac{v}{2L} = \frac{10}{2 \times 0.20} = 25\text{ Hz}. Since the vibrator frequency 100 Hz100\text{ Hz} is an integer multiple of f1f_1 (n=4n = 4), the string vibrates in resonance in its 4th harmonic with 4 loops, each having a length of 5 cm5\text{ cm}.)

Thus, the separation between successive nodes is 5 cm.