Physics of Equilibrium
I recently saw this picture on one of my friend's Snapchat stories. How is this water bottle able to balance on its side? The bottle is positioned so that its net torque is equal to zero. On the left side of the bottle, the force of gravity due to all of the infinitesimally small pieces of its mass on one side of the system's center of mass multiplied by the distance that their weight vectors are from the center of mass (AKA the counter clockwise torque) has some definite magnitude. On the right side of the bottle, the forces of gravity due to all of the tiny pieces of mass multiplied by their distances from the center of mass equals a net clockwise torque on the bottle. The counter clockwise torque and clockwise torques applied to the bottle are equal in magnitude and opposite in direction, causing the bottle to remain in rotational equilibrium. The calculus behind this situation is quite complicated, as you can probably tell.