Work = Force x Distance = 500 x 4 = 2000 Nm = 2000 J
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.
Because water is a very very very very very unusual substance ... It's
the only known substance whose solid form is less dense than its liquid
form near the same temperature.
In other words, water is the only known substance for which a solid lump
of it floats in a liquid glass of it.
If that were not true ... if the behavior of the density of water around its
freezing temperature were the same as the density of all other known
substances ... then life on Earth would be impossible.
Think about that for a while ! Ya gotta admire whoever it was that designed water !
