FORCES (Dynamics) Why do objects move?

A force is a push or a pull The unit for a force is a Newton Force is a vector. It has both magnitude and direction.

Categories of two forces Contact Forces (require physical touch) Non-Contact Forces (no touch) Frictional ForceGravitational Force Tension ForceElectrical Force Normal ForceMagnetic Force Air Resistance Force Applied Force Spring Force

5.1 Inertia Inertia is a term used to measure the ability of an object to resist a change in its state of motion. An object with a lot of inertia takes a lot of force to start or stop; an object with a small amount of inertia requires a small amount of force to start or stop. The word “inertia” comes from the Latin word inertus, which can be translated to mean “lazy.”

Newton's Second Law (Law of acceleration) The acceleration of an object is directly proportional to the force you apply and inversely proportional to the mass of the object.

Newton's Second Law If you apply more force to an object, it accelerates at a higher rate.

Newton's Second Law If an object has more mass it accelerates at a lower rate because mass has inertia.

5.2 Newton's Second Law Three forms of the second law:

5.2 Equilibrium The condition of zero acceleration is called equilibrium. In equilibrium, all forces cancel out leaving zero net force. Objects that are standing still are in equilibrium because their acceleration is zero. Objects that are moving at constant speed and direction are also in equilibrium. The bottom line: There is NO ACCELERATION in this case AND the object must be at EQUILIBRIUM (All the forces cancel out).

Free Body Diagrams A force diagram, which is also known as a free body diagram, is a sketch in which all the force vectors acting on an object are drawn from the center of the object.