Define force and give SI unit
A force is a push, pull or a twist which has a tendency to change the shape, state of rest or of uniform motion of the body on which it has been applied. In physics, a force is defined as an influence that causes an object to undergo a change in speed, a change in direction, or a change in shape.
When applied on a rigid object it change the state of rest or state of motion. And when applied to non rigid object it can changes the shape of the object.
where m is the mass of the object and a is the acceleration.
it's SI unit is kg m /s² or Newton.