Once you release the ball, you are no longer doing work on the ball. If you push as hard as you can on a wall, and the wall doesn't move, you aren't doing any work on the wall. Physicists calculate the amount of work done by multiplying the force applied by the distance in metres over which the force is exerted. Force is measured in units of newtons. To calculate work done you must be able to measure both the force applied and the distance over which the force was applied.
Gravity exerts a force on all objects.
The downwards force on a mass of 100  grams at the surface of the earth is 1 newton. This downwards force is called weight. If you were to be transported to the moon, your mass would stay about the same, but your weight would be a lot less. Make a device that can measure the amount of force applied to an object. Standard masses for calibrating your instrument can be made by adding sand to empty 35  mm film canisters or baby food jars.