Answer:
5 m/s
Step-by-step explanation:
The speed of a wave in a string is related to the tension in the string by the equation

where
v is the speed of the wave
T is the tension in the string
is the linear density of the string
We can rewrite the equation as

In this problem, the tension in the string is changed; however, its linear mass density remains constant. So we can write:

where:
T1 = 40 N is the initial tension in the string
v1 = 10 m/s is the initial speed of the wave
T2 = 10 N is the final tension in the string
Solving for v2, we find the final speed of the wave:
