I disagree.
Many substances show fluorescence under ULTRAVIOLET light, NOT microwaves. :)
I would say friction because it requires to surfaces in order for the force to take place
correct me if I'm wrong.
Answer:

Explanation:
Since the formula for kinetic energy of an object is:

Where m is the mass of the object and v is the speed. We can substitute m =
kg and v = 17900m/s:

You can do 50 and 10 and carry the 30 and it would be in the same power so you’ll have the same energy
vf ^2 = kx^2/m = 56(0.75)^2 / 2.5 = 12.6
Therefore, v= 3.5 m/s.