CBSE Class 9 Answered

There is an ambiguity about friction . It is not clear from image that friction is there or not.

Let us assume there is no friction because friction coeficient is not given.

Required retardation force to stop the moving mass is the product of mass and retardation.

To find the retardation we should know either how much time required to stop or how much distance is required to stop .

If we know either time or distance , we can calculate the retardation using the standard equations of motion.

Since neither time nor distance is given in the question, we can not solve this question .