No, I'm sorry; but that is not the right answer.

a = 10.0 m/s2 ?

This value of the acceleration is essentially "g", the value of acceleration during free fall. That means that if you cut the string, the hanging mass would fall just the same.

Always ask if your result is "believable" or "reasonable". Is is what you would expect?

(c) 2000, Doug Davis; all rights reserved.