In order for an object to accelerate, what must be applied?

Explanation:

According to Newton's second law of motion, the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.

Mathematically,    Force = mass × acceleration

or,                         Acceleration =

Thus, we can conclude that in order to accelerate an object, force must be applied. The object will accelerate in the direction in which force is applied.