Work: $W=Fs\cos (\theta )$

Energy is the ability to do work. Unit in $J$, Joules. Kinetic: $E_k=\frac{1}{2}m{v}^2$ Potential: $E_p=mgh$ Spring: $E_E=\frac{1}{2}k{x}^2$

Note: $\theta$ is for acting on a body at an angle. Mechanical energy is $E_k+E_p$.

In a conserved system, kinetic and potential energy exchange. Otherwise, they are lost.

Power is the rate work is done. $P=\frac{\Delta W}{\Delta t}=Fv$. Both are super useful.