Unit 8: Statics and Torque
What might desks, bridges, buildings, trees, and mountains have in common - at least in the eyes of a physicist? The answer is that they are ordinarily motionless relative to the Earth. Thus, their acceleration in the Earth frame of reference is zero. Newton's second law states that net F = ma,so the net external force is zero on all stationary objects and for all objects moving at constant velocity. There are forces acting, but they are balanced. That is, the forces are in equilibrium.
Completing this unit should take you approximately 8 hours.