Does gravity do positive or negative work on falling objectexplain? - Answers

It does positive work. There's 2 ways to look at this: 1) This one's a chemistry way. When work is done on a system by the surroundings, the work is positive. When the system itself is doing work on the surroundings, this is negative work. Just think of it in terms of the system. It gains energy when something does work to it and loses energy when it works on something else. Based on this, do you think it's positive or negative work? 2) This one's a physics way. W = Fd cos (theta). In this equation, W = work, F = a force, d = displacement, and theta = angle between the force and the displacement. So, let's take the example of a falling object. As it falls, the force of gravity is exerting a force towards the ground. The object is moving towards the ground also. Since both the directions are the same, theta is 0 and work is + (cos of angle 0 is +1). When the object is moving upward while gravity is acting on it, exerting a downward force, the angle between them is 180 degrees. At 180 degrees, cos is -1. Work done by gravity is negative in this case. Either ways, positive work is being done by gravity on the falling object.