Answer:
The maximum speed will be 26.475 m/sec 
Step-by-step explanation:
We have given mass of the toy m = 0.50 kg 
radius of the light string r = 1 m
Tension on the string T = 350 N
We have to find the maximum speed without breaking the string 
For without breaking the string tension must be equal to the centripetal force 
So 

So 


v = 26.475 m /sec
So the maximum speed will be 26.475 m/sec