JEE Main & Advanced
JEE Main Paper Phase-I (Held on 09-1-2020 Evening)
question_answer
A wire of length L and mass per unit length \[6.0\times {{10}^{3}}\text{ }kg\text{ }{{m}^{1}}\] is put under tension of 540 N. Two consecutive frequencies that it resonates at are: 420 Hz and 490 Hz. Then L in meters is [JEE MAIN Held on 09-01-2020 Evening]
A)1.1 m
B)5.1 m
C)8.1 m
D)2.1 m
Correct Answer:
D
Solution :
Fundamental frequency = 70 Hz. \[70=\frac{1}{21}\sqrt{\frac{T}{\mu }}\] \[I\approx 2.14m\]