For an body at rest, application of force causes a changed in its existing state and application of force on a body moving with uniform velocity would
give the body under consideration as acceleration

Newton's second law of motion is a relation between force and acceleration

Newton's second law of motion says that
" The net force on a body is equal to the product of mass and acceleration of the body"
Mathematically F_{net}=ma (1)
Where F_{net} is the vector sum of all the forces acting on the body

Above equation -(1) can be resolved along x,y and z components .Thus in component form
F_{netx}=ma_{x}
F_{nety}=ma_{y}
F_{netz}=ma_{z}

Component of acceleration along a given axis is caused only by the net component of force along that axis only not by the components of force along other
axis

Newton's second law of motion is completely consistent with newton first law of motion as from equation (1) F=0 implies that a=0

For a body moving under the influence of force, acceleration at any instant is determined by the force at that instant not by the previous motion of the
particle

Newton's second law of motion is strictly applicable to a single particle .In case of rigid bodies or system of particles, it refers to total external
forces acting on the system excluding the internal forces in the system.