What are the uses of astronomical perturbatio and what experiment can one create to test the acc. of g?

Answer 1

What a combination!
The primary use of astronomical perturbation is to detect the presence of another body near by, like the outer planets and other orbiting bodies of our solar system and distant stars that have dark stars and planets orbiting them.
The acceleration of gravity can be most easily tested by using a small dense body, like a lead weight and a pair of photo cells to start and stop a timer, although you could drop it a longer distance and try to time it by hand. One way to time without electronics would be to have a paper roll that is pulled by a motor at a speed that could be measured over a longish distance (say 3 meters). Then rig a way to release the lead weight and mark the paper at the same time (say a 1-2 meter stick with a pencil on it that would block the weight until the stick was pulled aside.) When the lead hit the paper, it would leave a mark and you could measure to determine the time it took to fall.