Can anyone suggest me some book/article explaining how and why the quantity named 'Energy' made its way into physics?
I have gone through "Lectures on Physics" (Vol. 1) by R.P. Feynman and have been convinced that at first scientists were in search of a quantity which remains constant w.r.t. any other internal change,in a closed system.The quantity later turned out to be 'Force x displacement'.
But we know that momentum is also conserved in closed systems. So why don't we invent a scalar 'mass x speed' (in order to fix the problem that momentum is a vector) and use this instead of 'Energy'? While we could take the advantage that 'mass x speed' is much simpler than '1/2 (mass x square of velocity)'.
One of my teachers, on being asked this question, said that energy is more fundamental than momentum. And giving the example of a field force, he wrote:
$$\vec{F}=\frac{\partial \varphi}{\partial x}\hat{\imath}+\frac{\partial \varphi}{\partial y}\hat{\jmath}+\frac{\partial \varphi}{\partial z}\hat{k}$$
And showed that the quantity $\varphi$ turns out to be the potential energy of a particle (e.g. a point mass in case of a gravitational field) in the field at the point $\vec r = (x,y,z)$. But what is the thought behind the approach to find out such a quantity whose change w.r.t. position will describe the force? And at which point 'Force x displacement' becomes more fundamental than momentum?
