Incomplete question.The complete one is here
A runner taking part in the 200m dash must run around the end of a track that has a circular arc with a radius curvature of 30m. The runner starts the race at a constant speed. If she completes the 200m dash in 23s and runs at constant speed throughout the race, what is her centripetal acceleration as she runs the curved portion of the track?
Answer:

Explanation:
Given data

Required
Centripetal acceleration
Solution
According to the motions equation the velocity given by:

The centripetal acceleration is given by:

Light waves are never 'aborted'.
They can be 'absorbed', and I think that's what you mean.
It's what happens when light hits something or goes into it,
and never comes out.
"Absorb" just means "soak up". When a light wave hits something and
gets soaked up in it, it's gone, and never comes out the other side.
The light wave certainly gets changed ... it no longer exists.
The object that absorbs it also gets changed. It soaks up the energy
in the light wave, and it has a little more internal energy (heat) than it
had before the light hit it.
Equal because the book is not moving and the forces are balanced/equal
Friction is the force that acts on an object and opposes its motion