Energy over one swing

You will follow the energy of a block on a spring through one period, and check that the total stays the same.

The idea. With $x = A\cos\omega t$, the velocity is $v = -A\omega\sin\omega t$. The potential energy is $\tfrac12 kx^2$ and the kinetic energy is $\tfrac12 mv^2$. Their sum should always be $\tfrac12 kA^2$.

Your tasks.

1. In omega, return the angular frequency $\sqrt{k/m}$.
2. In potential, return the potential energy of the spring at displacement x.
3. In kinetic, return the kinetic energy of the block at speed v.
4. In average_kinetic, the list ke holds the kinetic energy at many equally spaced moments of one period. Return its average.