What is the magnitude of the kinetic frictional force

Magnitude of kinetic force is the product of the normal force and the coefficient of kinetic friction.

Explanation:

The kinetic frictional force is the force which is experienced in the moving surfaces of bodies.The magnitude of the force is affected by the coefficient of kinetic friction between the material of two bodies in contact. Mathematically, it is expressed as;

Fk=μk*η

where;

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

the answer is b ) square root of 5