This is called "projectile motion". The projectile can be a baseball, a bullet, a golf ball, or a rock that somebody tossed. In this story, the swimmer is the projectile.
In projectile motion, the projectile is moving part horizontally and part vertically at the same time. The thing to remember about this kind of motion is: The horizontal motion doesn't change, but the vertical motion changes because of gravity ... just like an apple that fell from a tree.
The swimmer runs straight horizontally off the diving board. His horizontal speed is 3.62 m/s. He hits the water 1.68 m from the end of the board. How long did it take him to go that far ?
Time = (distance) / (speed)
= (1.68 m) / (3.62 m/s)
= (1.68 / 3.62) seconds
= 0.464 second .
(a). How high above the water was the diving board ? Well, the swimmer was falling for 0.464 second . The height is whatever it takes 0.464 second to fall.
Height = (1/2) x (acceleration of gravity) x (time)²
= (1/2) x (9.8 m/s²) x (0.464 sec)²
= (4.9 m/s²) x (0.2153 sec²)
= (4.9 x 0.2153) meters
= 1.055 meters .
(b). If the swimmer runs off the board slower, his horizontal speed is lower. That only affects how far out in front of the board he'll be when he hits the water. But his horizontal speed has no effect on how long it takes him to fall to the water. That's his vertical speed, and it only depends on gravity. No matter how fast or slow he runs off the board, or if he just stands there at the end and leans over until he falls, it takes him the same time to reach the water in every case.
It takes work to push charge through a change of potential. There's no change of potential along an equipotential path, so that path doesn't require any work.
<span>As per the second law of thermodynamics, when the energy gets converted from one form to another in a physical or chemical change, then the energy which we get as result of change is of lower quality or usability of such energy is less.</span>
