The speed of light in water is 2.25 x 108 m/s. What is true about the index of refraction of water? A. It is less than 1. B. It
2 answers:
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Answer:
Work can transfer energy between objects and can cause a change in the form of energy.
Explanation:
The best explanation can be done with an example.
Consider an apple of mass m falling from a tree. Initially, the apple is at rest on the tree, at a certain height h above the ground, so it has a form of energy called gravitational potential energy, equal to:
where g is the acceleration due to gravity.
As the apple falls, the force of gravity acts on it, and so this force does work on the apple. As a result, the potential energy of the apple is converted into another form of energy, kinetic energy, which is the energy due to the motion of the apple:
where v is the speed of the apple.
Consider another example: a man pushing a box along the floor with a force F. The man is doing work on the box, and this work is equal to
where d is the displacement of the box. As a result of this work, some of the chemical energy contained in the muscles of the man is transferred into the box and converted to kinetic energy of the box, which is put in motion and it gains a certain speed v. In particular, if there are no frictional forces involved, the work done by the man is equal to the kinetic energy gained by the box.