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- Homework Statement
- The block in figure has a mass M and descends with an acceleration a. The mass of the string below the point A is m. Find the tension of the string at the point A and at lower end.

- Homework Equations
- Newton's laws of motion.

**so I took string below point A and Block as a system. Taking mass of string below point A as m and mass of block M. Taking downward direction as X axis. I get Mg+mg-T, Taking T as tension by upward part of string. Now the question says about block descending with acceleration a.**

so again forces acting on system will be (M+m)a since it is going down. Total sum of forces will be

(M+m)g-T+(M+m)a = 0, so tension at point A will be (M+m)(g+a) = T.

but answer is (M+m)(g-a) = T.

so again forces acting on system will be (M+m)a since it is going down. Total sum of forces will be

(M+m)g-T+(M+m)a = 0, so tension at point A will be (M+m)(g+a) = T.

but answer is (M+m)(g-a) = T

What is it that I'm doing wrong?