A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency of 45 Hz. The mass of the wire is 3.5 × 10–2 kg and its linear mass density is 4.0 × 10–2 kg m–1. What is (a) the speed of a transverse wave on the string, and
(b) the tension in the string?
(a) Given,
Mass of the wire, m = 3.5 × 10–2 kg
Linear mass density, μ = m/l = 4.0 × 10-2 kg m-1
Frequency of vibration, f = 45 Hz
So, Length of the wire, l = m/μ
⇒ l = (3.5 × 10–2 kg)/(4.0 × 10-2 kg m-1)
⇒ l = 0.875 m
The wavelength of the stationary wave (λ) and the length of the wire are related as
λ = 2l/m
where, n = Number of nodes in the wire
For fundamental node, n = 1
∴ λ = 2l
⇒ λ = 2 × 0.875 m
⇒ λ = 1.75 m
The speed of the transverse wave in the string is given as
V = fλ= 45 m s-1 × 1.75 m
⇒ V = 78.75 m s-1
(b) The tension produced in the string is given as
T = v2μ = (78.75 m s-1)2 × 4.0 × 10–2 kg m-1
⇒ T = 248.06 N