Kinetic energy is the energy an object has because of its motion.
For acceleration of any object, we need to apply a force. After work done by applying force, energy will get transfer to the object, and the object will be moving with a new constant speed. The energy transferred is known as kinetic energy, and it depends on the mass and speed achieved.
Kinetic energy can be transferred between objects and transformed into other kinds of energy.
How we calculate KE
Consider a box of mass m being pushed through a distance d along a surface by a force parallel to that surface.
we know that we can substitute the acceleration if we know the initial & final velocity and the distance.
So, when a net amount of work is done on an object, the quantity which we call kinetic energy K changes.
Alternatively, one can say that the change in kinetic energy is equal to the net work done on an object or system.