1. Work is defined as the product of the force exerted on an object and the distance the object is displaced in the direction of the force. 2. Work is done when a force causes an object to move in the direction of the applied force, such as a girl pushing a chair. No work is done if there is no displacement in the direction of the force, such as a boy pushing a wall. 3. Work can be calculated using the formula W=Fd, where W is work in Joules, F is force in Newtons, and d is distance in meters. The document provides examples of calculating work done by various forces over different distances.