Work is defined as force causing displacement of an object in the direction of the applied force. The factors that determine the amount of work done are the magnitude and direction of force applied and the displacement it produces. Work is measured in joules in SI units and ergs in CGS units, where 1 joule equals 10^7 ergs. Positive work is when displacement is in the direction of force and negative work is when displacement is opposite to the direction of force.