Define 1 joule of work.

19 Explain the energy transformation of sun's radiation. 20 An artificial satellite orbiting the earth at an altitude of a few hundred kilometers loses a small amount of energy as heat due to friction of the thin atmosphere at that altitude. Why then does its speed increase progressively as it comes closer and closer to the earth? 2

What is the work done against gravity when a body is moved horizontally along a frictionless surface?

3

What is the condition for a force to do work on a body?