Work Done In Lifting and Lowering an Object
Now suppose we lift a particle-like object by applying a vertical force to it. During the upward displacement, our applied force does positive work on the object while the gravitational force does negative work on it.
In one common situation the object is stationary before and after the lift for example, when you lift a book from the floor to a shelf. Then are both zero.
Note that we get the same result are not zero but are still equal. Either way the result means that the work done by the applied force is the negative of the work done by the gravitational force.
apply to any situation in which an object is lifted or lowered, with the object stationary before and after the lift. They are independent of the magnitude of the force used. For example, when Gherkin made his record breaking lift, his force on the object he lifted varied ‘considerably during the lift.