Question

What is a kinetic energy?​

Answer 1

Kinetic energy is that a object possessed by its motion.

Answer 2

Kinetic Energy :- Energy Possessed by a moving object is known as Kinetic energy.

An object at rest has zero kinetic energy.

Energy is the capacity to do work. By work energy theorem, we say that :-

$\sf Energy_{final} - Energy_{initial} = Work \ done$

So, for a moving body, work done =

$\sf \tiny{Kinetic \ Energy_{final} - Kinetic Energy_{initial} = Work done}$

If, the object starts from rest, then kinetic energy at initial would be zero, this gives

$\sf Kinetic\ energy_{final} = Work done$

$\sf\implies Kinetic \ energy = Force \times \tiny{displacement} \\ \\ \implies K_E = F\times s \\ \\ \implies K_{E} = ma \times s \\ \\ \implies K_E = ma \times \frac{v^2}{2a} \\ \\(\tiny{since, F = ma \ and \ 2as = v^2 - u^2, and \ u = 0, since \ object\ starts\ from\ rest})\\ \\ \implies K_E = \frac{1}{2} mv^2$

Hence, formula for kinetic energy is half times of product of mass and velocity's square.