In Fig force `F` is gradually increased from zero Draw the graph between applied force `F` and tension `T` is the string . The coefficient of string friction between the block and the ground is `mu_(s)`

Explanation

As the external force `F` is gradually increased from zero , it is compensated by the friction and the string bears no tension when the limiting is achieved by increasing force `F` to a value till `mu_(s)mg` , the further increases in `F` is transferrred to the string
When `[(F lt mu_(s)mg, "the friction is static and"T=0,),(F gemu_(s)mg, T =F-mu_(s)mg,):}`