Answer:
870 N
Step-by-step explanation:
The expression for velocity of wave in a string is given below
v =
, T is tension and m is mass per unit length .
m = 45 x 10⁻³ / 30 x 10⁻²
= .15 kg/m
Putting the given values in the equation
76 =

T = 76² x .15
= 866.4
870 N approx.