1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution Initially , let the tension in spring be T Since hanging mass is just touching the weighing scale , T = 5g When elevator starts to accelerate upwards with acceleration 'a' , then on applying a fictitious force '5a' downwards and doing a force balance on the mass T + N = 5g + 5a N is the normal force from the weighing machine and T will not change So, N = 5a I am getting D) I.e data insufficient ,but this is incorrect . Given answer is B) . What is my mistake ?