I think it was either Robert Hook or Anton Van Leevwen Hoek
If the spaceship's Physicist happens to be hanging out of one side
of the ship, and he measures the speed of the photons as they pass
him and leave the ship, he'll see them passing him at 'c' ... the speed
of light.
When those photons pass somebody who happens to be in their
path, and he decides to measure their speed, he'll see them move
past him at 'c' ... the speed of light.
It doesn't matter whether the observer who measures them is
moving, or at what speed.
And it doesn't matter what source the photons come from, or
whether the source is moving, or at what speed.
And it doesn't matter what the photons' wavelength/frequency is ...
anything from radio to gamma rays.
The photons pass everybody at 'c' ... the speed of light.
Yes, I hear you. That can't be true. It's crazy.
Maybe it's crazy, but it's true.
Answer:

Explanation:
The roller coaster begins with maximum kinetic energy and no gravitational potential energy. The gravitational potential energy reaches its maximum when roller coaster is upside down at the top of the circle. The physical model for the roller coaster is constructed by means of the Principle of Energy Conservation:

The minimum velocity is:

Let assume that radio of curvature is measured in meters. Hence:


Here, K.E. = 1/2 * mv²
So, K.E. = 1/2 * (1200) * (24)²
K.E. = 1/2 * 1200 * 576
K.E. = 600 * 576
K.E. = 345,600 J
Hope this helps!