Mechanical energy is made when something is moved. The energy that is moving is kinetic. And potential energy is stored energy. Mechanical energy can be used to store energy and to cause moving energy. For instance: a slingshot. Pulling back the band creates potential energy and releasing it creates kinetic energy.
The light bulb converts electrical energy into light and heat.
Good luck! (:
Answer:

Explanation:
According to the free body diagram, in this case, we have:

Recall that the force of friction is given by:

Replacing and solving for the coefficient of kinetic friction:

We have an uniformly accelerated motion. Thus, the acceleration is defined as:

Finally, we calculate
:

You have not provided the diagram, therefore, I cannot provide an exact answer.
However, I will try to help by explaining how to solve this problem.
When light moves from air to glass:1- part of the light is reflected back into the air where the angle of incidence is equal to the angle of reflection
2- part of the light enters the water and refracts. The angle of refraction can be calculated using Snell's law.
In a diagram, the reflected ray would be the one getting back into air while the refracted ray would be the one entering the water.
You can check the attached diagram for further illustrations.
Hope this helps :)
Hydroelectricity is the best answer.
This is an article by the EIA, but the pie graph is the most helpful: https://www.eia.gov/energyexplained/?page=us_energy_home