1) Force may be defined as (a) the cause of motion (b) the cause of deformation (c) both a and b. 2) In ΣF= Ma, Fand a (a) are both scalars (b) are both vectors (c) form a scalar-vector pair. click here. 3) The direction of Fand ain ΣF= Ma (a) are the same (b) are different (b) are normal to each other.