What is Mechanical Equilibrium? A state where no physical changes occur (no change in motion) Net force is zero – Equilibrium rule:

What is Static Equilibrium? When an object isn’t moving, it’s in equilibrium.

What is Dynamic Equilibrium? When objects are moving steadily—not speeding up, not slowing down, not changing direction—they are in equilibrium.

Examples Find the missing force: 1.A 3N ball is hanging on a string. What is the tension in the string? 2.Two children push on a crate. They find that when they push together to the LEFT with forces of 155N and 187N, respectively, the crate slides across the floor at a constant speed. What is the force of friction (the force to the RIGHT)?

10-minute Practice Find the missing force (draw a free body diagram first): 1.A 50 N monkey hangs with each hand on a rope. The tension in one rope is 20N, what is the tension in the other rope? 2. Shaquanda and Tanya are trying to move a desk in Ms. Bates’ classroom. They each push on the desk to the right with a force of 40N. Lekan doesn’t want the desk to move. How much force will he have to push on the desk with to keep the desk at rest? **if you finish early you may work on your homework for tomorrow or help a classmate**