"Keeping a pencil standing on your hand" What physics topics should I research? Hi. My English is not perfect but I'll try my best. This is not a homework. It's a programming question for my simulator project. Scenario: - A pencil standing in your hand. It will fall or stand depending on how you move your hand. - Let's assume that the hand is just an ideal 'plane'. - Let's assume that a pencil is just a simple, ideal rectangular rigid body object. - *** Let's assume that a pencil will NOT fall on y-axis. Or in English: It will only fall to the left or right. Variables I have: - Real-time 'Acceleration' of my hand in x axis. (in m/s/s) - 'Mass' and 'Volume' of a pencil. Variables I need: - The change of 'theta'(angle) between the pencil and my hand(in x-axis) in each time slice. Or you could say d(theta) by d(t) Questions: What topic should I research for to relate the acceleration to the angle changes? note: *** Actually I want to do x,y and z axis but I think if I know how to solve one, I should be able to solve other too. Thank you in advance! Please let me know if I didn't provide enough information to the problem.