Question

The tension of a stretched string is increased by 69%. In order to keep its frequency of vibration constant, its length must be increased by :
A. 0.2
B. 0.3
C. `sqrt(69)%`
D. 0.69

Answer 1

Correct Answer - B
`l_1/l_2 = sqrt(T_2/T_1) = sqrt(169/100) = 13/10`
`l_1/l_2 = 1.3`
`(l_1-l_2)/(l_2) = 1.3 - 1 0.3`
`(Deltal)/(l) = 30%`