Question

mention the two factors by which the strength off the force is expressed

Answer 1

strenght of force depends upon mass and acceration of the object
force may be expressed by si unit newton
OR
cgs unit dyne

Answer 2

According to Netwon's second law:
we have F= mxa
∴ Force action on an object is directly proportional to product of mass and acceleration.
Two factors by which the strength of the force is expressed are :
--->Acceeleration
----> mass of the object
strength of the force is expressed by its magnitude.
F=mxa
=kg ms⁻² 
Magnitude of a force is expressed in SI unit of force called newton.
Along with magnitude of force, direction of force is also specified .