How to find the frictional force acting on an object (not the friction coefficient) ? ... ?

One can simply find the frictional force acting on an object using this equation:

(Ffrict = μ•F norm)

The process of determining the value of the individual forces acting upon an object involve an application of Newton's second law (Fnet=m•a) and an application of the meaning of the net force. If mass (m) and acceleration (a) are known, then the net force (Fnet) can be determined by use of the equation.

Fnet = m • a

If the numerical value for the net force and the direction of the net force is known, then the value of all individual forces can be determined.