Question

explain why it is easier to drive a Mat on floor when nobody is sitting on it but much more difficult to drag the same mat when a person is sitting on it

Answer 1

The friction between the mat and the ground increases in the second case which reduces the net force applied on it. This is because frictional force is directly proportional to the 'weight' of the body that moves with respect to a surface. So in the second case, the weight of the body (mat+Person) is higher and would have more friction that would oppose the motion.